Abstract. The terrestrial laser scanning (TLS) technique has been used to accurately reconstruct the 3-D shape of the walls and bastions of the historic city of Mdina (Malta) and underlying terrain. By applying this technique it has also been possible to extract additional quantitative information regarding weathering and deformational processes affecting the structures. Thus, with the aim of identifying the main instability mechanisms, a detailed 3-D crack distribution map has been drawn and the main displacement vectors have been defined.