Over the last few years numerous GPS networks in Italy have been installed and managed, mainly by local authorities and institutions. Therefore the GPS stations have been constructed with a variety of different monument types according to their needs and have been operated in fairly different environmental conditions, such as in towns or industrial regions, in the open country or mountainous regions. In this work we aim to assess the reliability and repeatability of the station positions and to study the noise property of different categories of GPS monument types. We analyze over 500 continuous GPS time series in Italy with a mean temporal length of 5.6 years. All the GPS observations were processed with the Bernese v5.0 software using a loose constraints approach. We include 45 sites in central Europe that are used as fiducial stations in the regional reference frame realization. After fitting a linear drift, offsets and annual sinusoids and after filtering a common mode movement of the whole network, the residual GPS time series represents the noise of each GPS station. We analyze the residuals using different power spectrum estimation schemes and estimate a power law noise model for each time series. The average noise characteristics are compatible with outcomes from earlier studies but we were not able to isolate distinct noise behaviors between different GPS monument types nor to ascertain a preferred monumentation, as far as noise amplitude and spectral indexes are concerned.