Palazzo Marchesale in San Giuliano di Puglia (Italy) is an old masonry structure hosting the new City Hall. It is quite complex and characterized by several parts with different height and foundation levels, arranged around an internal court. After the earthquake of October 31st (ML =5.4) and November 1st, 2002, (ML =5.3), the building was retrofitted and seismic joints were realized between the different buildings, in order to regularize its dynamic behavior. The structure has been considered for seismic monitoring in the framework of a research project funded by the Office for the reconstruction of San Giuliano di Puglia. In this context, seismometers were used to acquire vibration data under ambient excitation. The experimental results were used to define finite element models, by means of solid and shell elements. After material characterization, seismic analysis, linear and nonlinear, were done.