Cave and Karst Systems of Romania

Racoviţă, Emil Gheorghe (born November 15, 1868, in Iaşi, and deceased November 19, 1947, in Cluj) is a world-renowned Romanian biologist, the founder of biospeleology as a scientific discipline and of the world’s first speleological institute.

The “Emil Racoviță” Institute of Speleology (ERIS), first of its kind in the world, performing research activity for more than 97 years, owns its existence to the initiative of the great scientist Emil G. Racoviță (1868–1947), a biologist, polar explorer, and founder of biospeleology. The establishment of the ERIS became official when the Law no. 19.11 from April 26, 1920, was published in “The Official Monitor of Romania” (in Romanian: “Monitorul Oficial”) no. 86 from July 20, 1920. The institute was founded as an independent research unit within the Faculty of Sciences at the University of Cluj, and E. G. Racoviță served as Director and Manager between 1920 and 1947. The research trends initiated by E. G. Racoviță were continued until 1949 by R. Jeannel and P. A. Chappuis, two close collaborators of the Romanian scientist. In 1951, within the Geological Committee of the People’s Republic of Romania, two research groups were assembled in Bucharest and Cluj, respectively. Their mission was to prospect and identify phosphate deposits, an opportunity that led to the exploration of a large number of caves, which were simultaneously surveyed and investigated for their fauna.

Located at the southwestern end of the Trans-European Suture Zone (TESZ), the territory of Romania includes several major Alpine terranes of East European (Moldavian and Scythian platforms) or of West European affinity (Foreapulian, Getic, Euxinic terranes and the North Dobrogean Orogen). The pre-Alpine terranes from the basement of the Alpine terranes of West European affinity have a peri-Gondwanan provenance of Avalonian type (late-Neoproterozoic peri-Amazonian), Cadomian type (late-Neoproterozoic peri-North-African), or Carpathian type (essentially Ordovician, peri-North-African). Carpathian-type terranes were described in the Apuseni Mountains (Someș, Biharia, Baia de Arieș), in East Carpathians (Bretila, Tulgheș, Negrișoara, Rebra), and in the Getic Domain of South Carpathians (Cumpǎna upper unit of the Sebeș-Lotru Terrane, Leaota, Bughea, Caraș, Padeș, Fǎgǎraș). Cadomian type includes the Lotru lower unit of the Sebeș-Lotru Terrane. Drǎgșan and Lainici-Pǎiuș terranes from the Danubian Domain of South Carpathians, the Histria and Altȋn Tepe from Central Dobrogea, the east Moesia from South Dobrogea and Boclugea, Megina, Orliga, Uzum Bair from the basement of the North Dobrogean Orogen are all Avalonian type. The carbonate rocks are important in the basement of Baia de Arieș, Negrișoara, Rebra, Fǎgǎraș, and Lainici-Pǎiuș terranes. The Mesozoic carbonate rocks anterior to the Alpine terranes amalgamation cover significant surfaces in the Carpathians and Dobrogea, where Romania’s main karst regions occur. Karst-like features are also known on evaporites of Cenozoic age occurring in the Transylvanian Basin and Carpathian foreland.

Romania is not regarded as a country with an overabundance of karst resources, although it is home of many unique karst landscapes and caves as documented in the chapters of this book. Karst-prone rocks cover at least 5500 km2 (Fig. 1) representing ~2.3% of the total area of the country (238.397 km2). Worth noting is that the low percentage is mainly because extensive areas in which karst forming rocks exist, are covered by younger, Pliocene, and Quaternary age deposits.

Romania is a country with an old speleological research and caving tradition, despite the fact that the surface of the karst-prone rocks is very small.

The availability of groundwater in karst varies widely due to complex structure, geology, and degree of karstification. The karst aquifer system has an extensive network of interconnected joints, fractures, dissolution/solution cavities, within the carbonate group, that affect their capacity to store and transmit water from the land surface to springs. At the boundary between noncalcareous and karst formations, streams are sinking underground, generating caves.

Izvorul Tăușoarelor Cave, which held for many years the record for the deepest cave in Romania, is renowned for its steeply descending galleries, tectonic-controlled speleogenesis, and a rich assemblage of sulfate minerals (gypsum, mirabilite, arcanite, bassanite, epsomite, konyaite, leonite, and syngenite) that form a variety of speleothems. The enigmatic spherical concretions, known as “Tăușoare balls,” formed simultaneously with the limestone bedrock during its early diagenesis. The existence of hundreds of bones of cave bear (Ursus spelaeus) and brown bear (Ursus arctos) suggests the two species cohabited during the Quaternary in this part of the country. The cave represents the hibernation site for four bat species.

Vârghiș karst, with its limited spatial development but well-preserved features, is a peculiarity in the karst inventory of Romania. It shows several well-marked karstification levels, and a relatively high number of caves, the majority harboring thick clastic deposits. However, its most important asset is that it hosts numerous traces of past human occupation. For example, recent investigations of rock shelter Abri 122 produced one of the most significant Middle Paleolithic lithic assemblages for Romania, covering the time interval from Marine Isotope Stage (MIS) 5/7 to MIS 3. The occurrence of a volcanic ash layer within Bear’s (Ursului) Cave originating from the Ciomadul volcanic complex (East Carpathians) and dated to ~43/50 ka highlights the potential of Vârghiș karst in preserving such isochronous marker horizons, calling for further research.

Rătei Cave with its 7224 m length is located in the Leaota Mountains (South Carpathians). It develops in Middle and Upper Jurassic limestones and is formed by water enlarging post-Albian fractures. A small dam constructed near the cave entrance collects the water into a reservoir from where it is distributed for public supply. The water is calcium carbonate type, with a discharge between 40 and 115 L/s. The Rătei Cave stands out by erosional and dissolution morphology and a few speleothems.

Discovered in 1985 at an altitude of 2020 m above present sea level, the “Avenul de sub Colții Grindului” Cave (hereafter Grind Pit) represents Romania’s first Alpine-type cave included on the list of world’s deepest caves. With a depth of 540 m, the Grind Pit was for decades the deepest cave in Romania and has only recently been surpassed by the Vărășoaia cave system in the Apuseni Mountains. The cave develops in the Upper Tithonian limestones belonging to the Grind Formation. The highly tectonized, bedded limestone dips 75° to 85° toward east, and therefore, pit’s verticality is high. The origin of the pit is related to a massive tectonic breccia zone, formed during the uplift of the Carpathians, which is traversed by a fault that facilitated karstification. The stream flowing through the cave is recharging multiple karstic springs (medium flow: 400 l/s) located near the town of Zărnești, four kilometers away. The exploration activities are concentrated at −540 m in an effort to surpass the current terminus of the cave choked by a large boulder. The expected total vertical potential of the Grind Pit is 1270 m.

The Făgăraș Mountains consisting mostly of impervious metamorphic rocks are an unlikely location for karst development. Yet, due to the occurrence of a series of marble stripes interbedded within the metamorphic rocks, several caves developed in two areas in the central part of the mountains: Piscu Negru (at ~1200 m) and Mușeteica-Râiosu (between ~2100 and ~2400 m). Average air temperature is around 6.5 °C inside the Piscu Negru caves and 3.3 °C in Mușeteica. Cave No. 1 from the Piscu Negru Mine is the longest cavity in the massif (804 m), whereas M3-R2 Cave contains the speleothems from the highest altitude in Romania. Cave fauna is poor, and some bat species were found at the highest elevations of their habitat. The caves preserve reliable speleothem records for future studies on past climate variability and interactions between glaciations and karst.

The Polovragi Cave–Oltețului Gorge karst area is about 3 km2 in size and is traverse by the Olteț River through a spectacular narrow gorge, which represents the natural boundary between Parâng Mountains to the west and Căpățânii Mountains in the east. These mountains are part of the Southern Carpathian. Focul Viu Caving Club surveyed the Polovragi Cave between 1975 and 1985. In parallel with the survey activities in the main cave developed on the first level, several smaller caves were identified on both sides of the Oltețului Gorge. These caves are located on the second and third levels, which are interrelated with different peneplanation events that occurred in the Carpathians. In 2000, Focul Viu began working in the cave again, replacing gates, removing trash, digging to open new passages, and performing underwater explorations. By the end of 2011, new passages were found in the Hope Chamber and Costin Gallery, extending the total length of the cave to 10,793 and 92 m in vertical range. The Polovragi Cave along with two other smaller caves is presented in this chapter. The Polovragi Cave is the third longest cave in the Southern Carpathians and the eleventh in Romania. One of the smaller caves hosts an important bat colony, and the other one, with 800 m of passages, hosts Ursus spelaeus bones and deposits of saltpeter. The Bones Cave (Peștera cu Oase) located on the western side of the gorge (opposite side of Polovragi Cave) at a higher elevation is an old meander of the Olteț River.

Șura Mare Cave with its enormous entrance and 11,694 m of passages is the tenth longest cave in Romania and the fourth one with respect to its vertical range (+425 m). The karst system penetrated vertically and horizontally the entire sequence of limestone deposits of the Ponorici Cioclovina-Ohaba Ponor Plateau. Șura Mare Cave is known for its long underground stream, spectacular domes, and large well-decorated chambers. Dye studies performed in the early eighties prove the connection with Dosul Lăcșorului and Fundătura Hobenilor shafts, making this karst system one of the most important in Romania.

Răchiţeaua–Şipot cave system is one of the most complex and interesting underground feature in the Şureanu Mountains karst, and future speleological explorations will likely prove its scientific and hydrologic significance. It is composed of Răchiţeaua Shaft, a 2430 m long and 232 m deep stream cave and the Şipot Sump Cave, a 1270 m long river passage with six challenging sumps. Răchiţeaua Shaft is impressive through its vadose shafts, corrosion, and erosion features occurring especially along the main horizontal gallery, and also for the abundant speleothems (flowstones and rimestone pools) that mainly decorate the upstream tributary gallery.

The discovery of a Homo sapiens skull and a rich assemblage of rare minerals in Cioclovina Uscată Cave, along with a significant fossil ossuary in Cioclovina 2 Cave, the major hydrologic connection between Ponorici and Cioclovina cu Apă, complemented by the diversity and beauty of speleothems in Valea Stânii Cave, are just a few reasons why the Valea Stânii–Ponorici–Cioclovina cu Apă karst system represents a landmark for the Romanian karst. The scientific value of this karst region is topped by the numerous Dacian artifacts found at surface.

The Jiul de Vest, Lăpușnicul Mare, and Cernişoara rivers are in the western part of the Southern Carpathian Mountain Range. They form the natural boundary between the Retezat and Godeanu Mountains to the north and west, respectively, and the Vâlcan Mountains to the south. The Piule-Iorgovanu Mountains (Retezatul Mic Mountains) are between the Buta and Jiul de Vest Rivers and are an alpine karstic plateau (2000 m above sea level) of Jurassic limestones. On this plateau, an extensive network of dry valleys was developed and shaped by glaciers, which deeply eroded the carbonate (limestones) and noncarbonate rocks. Limestones are exposed from 710 m elevation at Cerna Spring (Izvorul Cernei) to 2080 m elevation in the Piule Mountain. Between the three rivers, hydrogeological connections have developed, supported by the continuity of the limestones and by structural-tectonic features. All three rivers contribute to the recharge of the most important karst spring in Romania, Cerna Spring.

The Pârgavului Cave is located in the Vâlcan Mountains (South Carpathians) and develops in Lower and Middle Jurassic limestones. Due to various carbonate facies, the dissolution acted selectively; thus, cave passages show different morphologies. The Mesozoic tectonics events combined with the hydrogeological conditions existing during the Quaternary, created a unique imprint on various geomorphological aspect of the cave. Speleothems are present in the sub-horizontal part of the cave. The progressive incision of the underground river led to the formation of several generations of shelfstones.

Since both caves developed in similar geological and hydrogeological conditions, they are presented in this chapter side by side. Although very different in size, both caves are well-known for their wide diversity of speleothems. Cioaca cu Brebenei is an 85 m long cavity that hosts some of the largest and most spectacular helictites of the Romanian karst. The cave has been carved by the Izvorele Creek, a right-side tributary of the Motru River. Cloşani Cave is one of Romania’s most thoroughly studied caves that hosts the only underground laboratory devoted to a variety of “in situ” cave studies. The cave has two major galleries (Laboratories and Crystals) summing up 1458 m of passages. Abundant and diverse speleothems, including shields, draperies, eccentrics, helictites, and gorgeous calcite pool spar crystals, are decorating the Crystals Passage. Cloșani appears to be a base-level cave, genetically connected with the flow of the Izvorele Creek and at a later stage of the Motru River. U-series analyses of speleothems indicate the cave is older than 600,000 years. Both caves are speleological reservations (Protection class A) located within the Domogled-Valea Cernei National Park and the ROSCI-0035 (Romanian Sites of Community Importance) “Natura 2000” Site.

Martel and Lazului are active phreatic/epiphreatic caves with a superimposed vadose morphology. Martel is a branchwork cave developed parallel with the river as a left (north) side meander and is located at about 8 m below the thalweg. The water level in the cave rises and falls along the main gallery, where the lakes/streams at the lightest rain become sumps. The cave is relatively poor in speleothems, except the fossil gallery (CS FV Gallery of Memories) located at the upstream end of the cave, but numerous erosion and corrosion features are present. Lazului is also a branchwork cave, forming a large meander on the right (south) side of the Motru Sec River, where at the lowest points of the cave, five streams are disappearing underground. Erosion and corrosion features are present, and speleothem is found occasionally in the upper level of the cave.

Isverna Cave is situated on the eastern slope of the Mehedinți Mountains, at an altitude of 450 m. It is over 4 km long, and it functions as the water collector for a karst area of over 20 km2. It is traversed by a river with very clear water except during flood conditions. A series of sumps, of which the longest is the Black Sump (~700 m), are spread along the underground river. This makes the cave an excellent destination for cave diving activities. The first few hundred meters of galleries host hibernation and maternity bat colonies.

Ascunsă Cave is situated in the Mehedinţi Mountains and is part of the Isverna cave system. The cave was discovered in the late 1970s by members of the Focul Viu Caving Club, who surveyed the first 13.5 m of it. Since 2008, the “Emil Racoviţă” Institute of Speleology and the Underwater and Cave Exploration Group explored and surveyed 691 m of passages totaling 185 m of vertical development. Studies based on stalagmites from this cave revealed the climate evolutions during the last glacial cycle.

In the central part of the Mehedinţi Plateau, west of the Nadanova-Baia de Aramă tectonic corridor, Zăton and Ponoarele depressions, along with Bridge’s and Bulba caves form a karst system developed in Mesozoic limestones. The Zăton Lake hosted by a karst marginal depression is located on Precambrian granitoides rocks, with its northeastern part in Mesozoic limestones. Dry for most part of the year, the lake fills after heavy rains or snow melting and is drained along the subterranean galleries of Bulba Cave (5360 m long). When the Zăton Lake is full, the water level rises and flow through the Bridge’s Cave, flooding a large sector of the cave, forming a pond hydrodynamically connected to the Zăton Lake. Once the lake level recedes or dries out, the underground pond disappears. During years with heavy rainfall, a second temporary lake forms within the Ponoarele endorheic depression, which also drains along the underground network of the Bulba Cave. The Bridge’s Cave, 734 m in length, presents an underground network consisting of dry galleries, galleries temporarily invaded by rising waters from below, and underlying—only partly accessible—galleries with perennial flow. Vertical shafts connect the passages with perennial flows, to overlying galleries. Bulba Cave is the local base level, which control the evolution of the entire karst system. In the central sector of the dry galleries, calcite draperies, soda straw, and candlestick stalagmites are common. Both caves host bat colonies, represented by the species: Rhinolophus ferrumequinum, Rh. hipposideros, Rh. blasii, Miniopterus schreibersii, and Myotis dasycneme.

Epuran-Topolnița karst system develops in the central-southern part of the Mehedinţi Plateau, in the vicinity of Jupânești and Marga villages, along a geological structure represented by a lower Cretaceous narrow limestone stripe oriented NNE-SSW. The underground drainage of the Topolnița, Ponorăţ and Peţimea streams generated spectacular, large-sized caves developed on several levels, such as Epuran (3.6 km) and Topolnița (22 km). The Epuran Cave is located on the western side of the limestone band, in the highly tectonized wall of a closed depression and presents two tiers of galleries. The upper, dry (fossil) level has a series of wide and narrow spaces, abundantly decorated by speleothems (stalagmites, flowstones, curtains, rimstone pools and cave pearls. The stream passage (lower level) is a labyrinth, characterized by breakdowns, clay deposits and marks indicating the water levels on the walls. Topolniţa Cave is the main collector in the area, the underground network being developed on five distinct levels, with large galleries and rooms, rich in speleothems and gigantic blocks collapsed from the ceiling. The cave presents multiple entrances, but the most spectacular one is Gura Prosăcului, a hydrogeological break into the limestone band by the Topolniţa River.

Over 300 dry (fossil) and active (stream) caves of thermal and hypogene origin are known in the upper Cerna Valley, between Naiba Valley and Pecinișca Village. The large variety of caves is sustained by a complex geology developed along the graben, with granites outcropping along the Cerna River’s thalweg. The presence of this granitoid pluton is the source of a large geothermal anomaly in Băile Herculane area and a smaller one 21 km north, where two thermal springs are located. A synthesis of the Focul Viu Caving Club explorations, emphasizing the Great Cave of Șălitrari (the longest cave in the area) and Ogașul Adânc, a stream cave that traverses the limestone strip, is presented in this chapter.

Several small caves located in the southwestern part of the South Carpathians discharge steam or/and chloride-rich hot groundwater derived from a geothermal reservoir situated nearby. The monitoring of natural tracers (heat, certain solutes, stable isotopes) documented uncommon levels for the fluids discharged within the Băile Herculane caves, thus revealing flow processes that ordinary meteoric-derived groundwater would be unable to depict. Furthermore, the exotic cave minerals and their isotopic composition suggest that the caves are the result of combination of hypogene and epigene processes. A rich and peculiar endemic troglobite fauna was identified in the Adam’s Shaft, in which a guano accumulation dated to ~8425 cal yrs BP suggests it is one of Europe’s oldest permanent bat colonies. The unusual warm/wet microclimate of the cave favored both an ideal roosting site for bats and a “tropical” biospeleological oasis.

The Captare Cave (Peștera de la Captare) is located in the western part of Romania (Banat), in the sedimentary zone Reşiţa-Moldova Nouă, which host the largest single exposure of limestones in Romania (~800 km2). The stream from the Captare Cave is a right (south) side tributary of Miniș River that crosses from northwest to southeast the northern/upper section of the carbonate rocks. This chapter focuses on the explorations of the cave, including the recent (since 2013) scuba diving activities, which resulted in the discovery of three major galleries (Chámovod, Never-ending, and Broken Lines Corridors), which increased the length of the cave from 961 to 2900 m.

Ponor-Plopa is a tiered karst system developed along a small underground stream that includes five sumps. While part of the system was known and visited for a long time, the sections located beyond the sumps were only explored in the last decades. These sections became known for their rich paleontological deposit, including remains of cave bear and other large carnivores and herbivores that have been accumulated within some passages c. 50–30 ka ago. The cave is internationally known for yielding the oldest remains of a modern human (c. 40 ka) that has shown proof of admixture with Neandertalians.

Buhui Cave in the central part of the Reșița-Moldova Nouă karst region (Aninei Mountains) has a total length of 7429 m, of which 2100 m are represented by the main meandering stream passage that hosts spectacular vadose and phreatic morphologies. The cave has multiple entrances and includes a number of well-decorated chambers, in one of which remains of Ursus spelaeus and Capra ibex (Steinbock) were identified.

Comarnic Cave is situated in southwestern Romania, in a region in which the Mesozoic limestones cover an area of ~600 km2 and form parallel ridges with high plateaus that are fragmented by deep gorges. The karst plateaus are dotted by sinkholes and sinking streams that recharge permanent or temporary karst springs. Comarnic Cave (6201 m) represents a hydrological penetration of the Ponicova Creek across the Upper Jurassic–Lower Cretaceous limestone bar. Its passages are mostly descending and develop on three levels (inactive, temporarily active, and active), with an offset of 101 m between the access points. The upper (inactive) level is rich in speleothems, such as draperies and stair-stepped rimstone pools, well developed in the Virgin Chamber. Along the lower level, erosional and/or solutional features are abundant. Comarnic Cave is well known for its spectacular chert layers (in the Zebras’ Chamber) protruding from the limestone along the bedding planes. Adventure caving trips can be arranged at the Semenic-Cheile Carașului National Park Headquarter.

The Exploratorii 85 Cave with 5120 m of passages is one of the largest underground cavities of the Bănăţean karst, which is located in the western part of the Southern Carpathians. Discovered in 1985 by I. Marius, with Exploratorii Reşiţa Speleological Association, it was intensively explored and surveyed until 1987. The cave is formed by upper-level well-decorated fossil galleries and a lower level with 5 underground streams that come out in the Caraş River, near Racoviță Cave. Dye studies show that the cave potential is about 10,000 m. The cave is in custody of the Exploratorii Reşiţa Speleological Association.

Poiana Gropii with 1900 m in length and −249 m depth is the deepest vertical cave in Banat region formed by vadose water flowing along fractures and bedding planes. Speleothems are present only below −130 m, but spectacular morphologies due to erosion and corrosion occur throughout the cave.

Zidită Cave distinguishes itself from other caves in the region due to the archaeological artifacts discovered in the sediments accumulated at the cave entrance, the paleoclimatic information recorded in the cave’s sediment, and longtime hibernacula and nursery for several bat species.

Some of Romania’s largest and most interesting cave systems are located in the Bihor Mountains. Among these, Dârninii Cave is one of them and excels through its length (5645 m) and size of the passages/rooms, as well as some of the speleothems (columns, domes). To date, the scientific research comprises some studies on cave minerals, fauna, underground climatology, and microbiology. Although scanty, all these investigations point out to some very intriguing cave resources that await future detailed studies.

Zgurăști–Poarta lui Ionele (Gate of Ionele) cave system totals 5809 m (5424 + 385 m) of passages and is located in the Bihor Mountains in NW Romania. It includes the Zgurăști Cave, renown for a series of lakes perched at ~118 m above Ordâncușa River and Poarta lui Ionele Cave, a part of which is open for tourists. The cave system has been formed by an underground river that was once recharged by waters of the Mununa limestone plateau under which it is formed. The final part of the Zgurăști Cave is clogged by rock debris and clay, generating the largest underground lake in Romania. Presently, the water appears in Poarta lui Ionele Cave and flows into Ordâncușa River. Poarta lui Ionele Cave houses a bat nursery of Miniopterus schreibersii.

One of the main underground drainages in the Gârda area (Bihor Mountains) is Coiba Mică–Coiba Mare–Tăuz cave system, which holds several unique records in the Romanian karst: (1) Coiba Mare has the widest cave entrance (74 m) and the deepest dived sump (Lake of Death, −92.5 m), (2) it includes the first underwater cave junction made between Coiba Mare and Coiba Mică, and (3) Tăuz is regarded as one of the most beautiful karst springs and held the depth record for many years.

One of the most important karst regions of western Romania is Bihor Mountains, which form the central part of the Apuseni Mountains. The centerpiece of Bihor Mountains is Padiş Plateau developed at about 1000–1200 m altitude and characterized by numerous karst features as dolines, ponors, springs, and caves. Cetățile Ponorului is traversed by a stream that disappears in a sump at the end of the cave to resurface in Galbena Spring. Vărășoaia cave system (V5) with −653 m is the deepest, whereas Humpleu-Poienița is the second longest (36 km) in the country. Another highlight of the Bihor Mountains karst is world’s largest and oldest perennial ice deposit in Scărişoara Cave. Some of the oldest cave paintings in Europe have been discovered in Coliboaia Cave which along with the Secăturii Hill form a cave system. In Vârtop Cave, three Neanderthalian footprints were preserved in a hardened calcite moonmilk deposit, while the Bears Cave (Peștera Urşilor) is known for several cave bear skeletons in anatomic connection. Some of these caves are presented below or in separate chapters of this book.

Drăcoaia Cave was known and visited by local people and tourists for a long time. The cave has an impressive entrance (15 × 12 m, width × height), which continues with a slightly ascending passage that ends after 150 m in a massive flowstone obstruction. The exploration activities conducted by Slovak cavers between 2002 and 2015 led to significant new discoveries in the cave, which now reaches 1963 m in length and a total vertical relief of 107 m. Cave consists of two levels of vadose canyon passages with sub-horizontal gradient, which are interconnected by steeply inclined meandering passages. Cave was formed by sinking streams draining from overlying non-karst Permian rocks. It hosts an endemic species of springtail, Megalothorax draco.

Vărăşoaia cave system (VCS) was discovered in 1986 in the Bihor Mountains of Western Romania, under the Padiş Plateau. After countless rounds of in-cave blasting aiming to overcome some very tight passages, the cavers managed to intercept a complex karst system with several very large active (carrying underground streams) and dry galleries and reached the −653 m in depth. To date, VCS is the deepest explored cave of Romania. The network currently has over 25 km of mapped passages, but explorations are still underway. Due to floods risk and high collapse possibility in some cave sections, visiting permits are granted only to experienced cavers.

Valea Rea Cave in the Bihor Mountains of Western Romania contains large chambers, passages with distinctive morphology, and abundant and beautiful speleothems in which 33 minerals were identified. We found evidences for both hypogenic and epigenic speleogenetic processes contributing to the origin of the cave. With a known length of over 16 km and a depth of 384 m, Valea Rea overshadows most of the other caves in the country, and emerges as one of the mineralogical treasure of the world.

Humpleu Cave is currently Romania’s second longest cave. Its highlights are the beauty of its fossil and water passages, the alpine-type narrowness of the second, vertical, entrance, and by the still exciting possibility of finding new passages. Except for a number of mineralogical studies, Humpleu Cave remains largely under-investigated. A variety of features (morphology, tectonics, speleothems, speleogenesis) are awaiting to be studied in order to better understand this huge cave and its surroundings. The present chapter gives a very brief and condensed overview of the cave and hopes to resuscitate interest to study it more thoroughly.

Vaşcău Plateau hosts one of the most spectacular doline fields with karst lakes and ponors in the Romanian karst. The karst landscape is completed by over 70 short caves and shafts, including Câmpeneasca Cave with its spectacular waterfall at the entrance, the Iliei Pit the deepest (−165 m) cavity in Codru Moma Mountains, and last but not least, the Călugări intermittent spring.

Meziad Cave is known and studied since the late nineteenth century and has been developed for tourism at the beginning of the twentieth century. Today, part of its natural and cultural heritage revealed by scientists and cavers can be visited by tourists along a 1500 m path. Most of its chambers and passages are restricted to research for protection and conservation purposes. Meziad Cave is a landmark of the Pădurea Craiului Mountains (Apuseni Mountains, northwestern Romania) due to its diversity of scientific, aesthetic, and recreational values, such as: particular morphology characterized by huge voids, rare phosphate minerals related to the guano deposits, massive wind-controlled stalactites, some of the largest bat colonies in Romania, diverse and endemic subterranean fauna, and valuable paleontological and archeological remains.

Pădurea Craiului has the largest plateau-type karst in the Apuseni Mountains developed at about 500–600 m altitude with numerous karst features as karren, dolines, ponors, springs, and caves. In the southern part of the plateau, Ciur Izbuc–Ciur Ponor–Topliţa de Roşia karst system includes two distinct caves. Ciur Izbuc is a through cave traversed by a stream that disappears in the middle of the cave to resurface in Ciur Ponor–Toplița de Roşia Cave. The highlights of the system are the Bears Gallery (Galeria Urșilor) and the Footprints Hall, which housed many skeletal remains of cave bear and about 400 footprints as old as 27–31 ka. Ciur Ponor–Topliţa de Roşia is the longest through cave in Romania, with a stream that runs from Ciur Ponor entrance to Topliţa de Roşia Spring passing through large chambers with their floor covered with alluvial sediments and breakdown blocks and large passages and sumps in between. In the northern part of the plateau, the underground stream traversing Bătrânului Cave resurfaces a few km downstream in Vadu Crişului Cave ending its journey with a spectacular waterfall in the south bank of the Crişul Repede River.

Stanul Foncii is the deepest shaft (−339 m) in the Pădurea Craiului karst with a total of 4106 m of passages. It is a typical vertical cave formed by vadose water flowing downward along large fractures or at intersecting fissures. The presence of smooth and sometimes rilled wall morphologies in all eight shafts is indicative of dissolution by calcite-undersaturated groundwater descending into the cave. Speleothems were encountered only in the Parallel System, where bones of Ursus spelaeus are also present.

Despite its modest appearance and relatively difficult to explore fossil section, the underwater part of the Izbândiş system makes this cave special, as it hosts the deepest sump in Romania (−105 m). Besides, archeological findings in this cave had helped understand the spread of the Igriţa-type culture and its distinctive objects. The cave is also shelter for five bat species (Barbastella barbastellus, Myotis myotis, M. oxygnathus, Rhinolophus hipposideros, and Rh. ferrumequinum) and habitat for eleven insect species.

Peștera Vântului lies in a ~200-m-thick middle Triassic limestone and is the longest cave in Romania, with a surveyed length of over 50 km and vertical extent of 162 m. It is a multi-level cave, which consists of passages that are mainly sinuous tubes and canyons having their floor covered with alluvial sediments and breakdown blocks. Vadose flow is present in the lowest level of the cave, where significant amounts of black iron–manganese-rich deposits coat the gravels and the cave walls along the underground stream. Fourteen oxide and hydroxide minerals have been described in their composition, with braunite first documented in a cave environment worldwide. Gypsum speleothems are abundant particularly along the upper levels 1 and 2. Typical for Vântului Cave is its deep meandering canyons, which are best displayed in the Racoviță Meanders section of the second level. From a speleogenetic point of view, it is a base-level cave, having its all four major levels developed in the epiphreatic zone, later connected in between by vadose canyons and shafts.

Măgurici Cave in the Someş Plateau of NW Romania hosts a large deposit of bat guano. Pollen and stable isotope investigations on this cave material provide meaningful information regarding the paleoclimate and paleoenvironmental conditions over the past 1200 years. Apart for some gypsum crystals, the cave is deprived of spectacular speleothems, but it contains nodules, crusts, and earthy masses in whose composition eight phosphate and four sulfate minerals were identified.

Movile Cave (SE Romania) is the first known subterranean chemosynthesis-based ecosystem. Sulfur- and methane-oxidizing, as well as nitrifying microorganisms, form the base of the food web in this peculiar ecosystem. The bacteria use mainly oxygen from the cave’s atmosphere as electron acceptor to oxidize H₂S, CH₄, and NH₄+, which originate from the deep thermomineral aquifer. These microorganisms form microbial mats that cover the water surface and the cave walls adjacent to the water. For cave standards, this is an unusually abundant primary production that allows 51 invertebrates species to thrive here. Of these, 35 are endemic to this ecosystem and display advanced troglomorphy. Numerous aquatic and terrestrial species graze on the rich microbial mats present in the lower sections of the cave, while others predate on protozoa and smaller invertebrates. Speleogenesis in the Movile Cave area was initiated in the Late Miocene and continues today by the action of the sulfuric acid resulted from the oxidation of sulfide in the lower part of the cave. The cave was sealed off during the Quaternary by thick and impermeable layers of clays and loess.

Limanu Cave is a network maze situated in the southern part of the Dobrogea Plateau (SE Romania), close to the Black Sea coast. It is hosted in Sarmatian (Kersonian) lumashelic and oolithic limestones, interbedded with marls. The total length of its passages is close to 3.5 km, and it preserves evidences of important human impact on its wall morphology. Throughout the cave, human intervention can be identified in the form of carving of walls and ceiling, as well as the buildup of walls made of stacked limestone slabs. Mineralogical data reveal an important presence of magnesian calcite and dolomite. The cave is a Site of Community Importance (ROSCI0191) and hosts the last colony of Rhinolophus mehelyi in Romania, which gathers ~100 individuals, in a steep decline from ~5000 individuals reported from Dobrogea in the 1960s.

Evaporite karst in Romania is mostly related to Miocene occurrences in the intra-Carpathian Basins, Subcarpathian Nappe, northern Dacian Basin and, to a minor extent, the Eocene in the NW Transylvanian Basin. Evaporitic karst areas account for 259 km2 (salt karst 48%, gypsum and anhydrite karst 52%). The most typical landforms are: dolines, karren, and caves. Until now, 53 salt and 20 gypsum and anhydrite caves, respectively, were recorded in Romania. The salt karst from Meledic Plateau (Mânzălești, Vrancea region) records the highest number of caves (47) and karst landscape complexity, followed by the Praid–Corund and Slănic–Prahova salt mountains. Romania’s most notable evaporite endokarst feature is the 3234-m-long 6S Cave from Mânzălești. Karren morphology is sharp-edged, particularly dominated by rills, runnels, and straight wall channels. Mining and controlled flooding of abandoned mined chambers have significantly influenced the evolution and functioning of salt karst systems by formation of anthropogenic saline lakes and new active underground conduits (Slănic-Prahova, Ocna Mureș). Solution of gypsum and anhydrite has a more discrete imprint on the related karst landscape, outlined in the Meseș Mountains, Turzii Gorge, Tazlău Subcarpathians, Maramureș Depression, and Hunedoara Basin. Dolines and karren are the most prevalent exokarst landforms in gypsum, whereas caves are short (up to 30 m) and speleothems rather poor.

Romania hosts some of the largest salt deposits in Europe, most of them located in the Eastern Carpathians and the Transylvania Depression. These are thick Miocene age evaporates precipitated in a lagoon facies. Since the end of the eighteenth century, geologist extensively mapped the salt deposits for mining purposes, gaining worldwide recognition. In fact, the term diapir was introduced in the geological literature by the Romanian scientist Ludovic Mrazec in 1906. The karst formed on evaporite rocks represents about 5% of the Romania’s exposed karst and is located mostly in the lowland hills of Eastern Subcarpathians Bend. The salt outcrops on ~150 km2, just 0.06% of Romanian territory. A few details about Meledic Plateau, which is part of the Buzău Land Geopark, and the Slănic Prahova Salt Mine, are the subject of this brief chapter.

Ice caves represent a unique karst environment in which the morphological characteristics of cave passages influence the underground air circulation to such a degree that allows large perennial ice deposits to accumulate and be preserved for thousands of years. Scărişoara in the Bihor Mountains hosts the largest and the oldest ice deposit documented in a cave worldwide and is probably the world’s best investigated ice cave.

The chapter presents an updated list of all minerals occurring under various settings in caves from Romania.

Evidences show humans must have entered caves in Romania prior to 65,000 years ago. Their interest in mining activities came, however, much later, with the first documented signs predating the arrival of Romans in Dacia (present-day Romania), in the second century BC. Although writings about minerals in Romanian caves date back to the eighteenth and nineteenth centuries, the first scientific texts on minerals found in caves discovered during mining and quarrying activities only appeared after 1850s. From a mineralogical point of view, two distinct categories are recognizable: (1) caves displaying speleothems of ordinary carbonate mineralogy and (2) caves with unusual mineral paragenesis. The latter group could further be subdivided into: (i) cavities located near or within nonmetalliferous or polymetallic ore fields, (ii) skarn-hosted caves, and (iii) caves in which H₂S-rich thermo-mineral waters discharge. The study of these caves resulted in the discovery of minerals, either new for science (ardealite) or to the cave environment (anhydrite, burbankite, foggite, ikaite, konyaite, etc.). However, the scientific relevance of those caves discovered in mines and quarries, along with the mined caves, is not restricted to mineralogy but also encompasses anthropology, archeology, Quaternary geology, biospeleology, karst science (speleothems, speleogenesis, etc.), and tourism.

An overview of Romanian cave fauna with the most important achievements in historical biogeography, diversity, ecology, phylogeny, and conservation is presented.

A review of the research and protection on bat fauna in the Romanian caves has been conducted. A few relevant arguments are given as to why the most abundant bat colonies in the European Union are located in Romania. Of the 31 bat species in Romania, 28 use caves as shelters, especially in the hibernating period. Over 100,000 (up to 170,000) individuals were counted in two of the 70 caves that are considered shelters of major importance. A group of five important caves and also several smaller others, along with the natural habitats in the area, form a bat hot spot in south-western Romania.

The archaeological research of the substantial and diverse Romanian karst has a long history going back to nineteenth-century antiquarians. A more systematic interest emerged, however, in the interwar times and continues to the present day. The earliest proof for the human use of caves in the Romanian Carpathian area belongs to the Last Interglacial Neanderthals, but Last Glacial Mousterian presence was also reported. They all indicate short-lived and possibly recurrent excursions into generally low mountain environmental settings (<1000 m) in search of local game. Despite spectacular palaeoanthropological (including the earliest Anatomically Modern Humans in Europe) and parietal art finds, the intensity of cave use by Upper Palaeolithic hunter-gatherers (Aurignacian and Gravettian) was surprisingly low, with most consistent occupations dated only to the final stages of the Pleistocene (Epigravettian/Epipalaeolithic). The small Upper Palaeolithic inventories in caves indicate very short, exploratory stops that correlate to the documented focus of these communities on open-air settings at lower altitudes. From Mesolithic to Medieval times, caves were used with varying intensity, serving as temporary/seasonally residence, as well as for ritual or economic purposes. Thick Early Neolithic cultural sequences, occasionally spectacular Bronze and Iron Age depositions, much like the Roman and Palaeo-Christian finds are particularly telling for the important residential and ritual/religious role some caves played. Through time, apart from their topography and degree of accessibility, the importance granted to these natural shelters by the various communities depended on the continuous change of the sociocultural and economic contexts.

From prehistoric times, caves have been used as shelters and places for cultural, religious, and ceremonial manifestation. There is no ancient culture that does not mention in its history at least once “the afterlife,” “the other world,” or “the underground world.” Starting with the eighteenth century, cave exploration and research began to reveal the subterranean beauty in all its elements: geology, biology, paleontology, archeology, and hydrology. In the last century, people started to use the caves for touristic purposes. Over the past decades, the concept of sustainable use of natural and cultural heritage has been introduced in show caves management to protect and preserve their heritage for future generations. In Romania, more than 12,500 caves have been discovered and explored. The first cave that opened its gates for tourism was Meziad Cave in 1903. Today, Romania has seventeen show caves, all included into a national protected area network. Apuseni Mountains and South Carpathians host most of the show caves of Romania, seven and eight, respectively. In these caves, the visitor has the opportunity to explore the ancient history of Europe and the today’s beautiful subterranean landscapes. Some show caves (i.e., Muierii, Ungurului, Meziad) are emblematic for the distant past, with traces of human activities or skeletal remains ranging in age from the Paleolithic to the Neolithic. Scărișoara Ice Cave allows the visitors to discover one of the world’s largest and oldest ice blocks, whereas Urșilor Cave is known for its important fossil assemblages, among which a cave bear skeleton in anatomic connection that is ca. 40,000 years old. All show caves of Romania host peculiar fauna and unique landscapes, and discovering their natural and cultural heritage while enjoying the beauty of the natural protected areas that host them is an experience worth taking.

Presently, Romania experiences a substantial expansion of the so called speleological tourism in protected caves and opening of new caves with and without touristic infrastructure for which impact studies are of questionable quality or absent. These, along with the lack of microclimatic and biological monitoring, are the three main factors that jeopardize the protection of caves and their natural heritage represented by speleothems, sediments, rare minerals, human and animal fossils, endemic living fauna, etc. This chapter is the result of almost 100 years of experience gained in the study of caves by the researchers of the “Emil Racoviță” Institute of Speleology in Cluj and Bucharest and wishes to draw attention on the problems of Romanian caves protection and to point on some future directions to be followed in order to stop the actual destructive tendencies.

This document presents a brief description of methods, instruments and grading for a cave survey. It is intended to show to the present and future generation the way the caves were surveyed at the end of the XXth centuries, and what instruments were used the most. More then likely the new cave maps resurveyed with digital instruments will find discrepancies in the length or vertical development of a cave, but we did our best to do a good job with the technology available in that time.