This paper describes the preliminary results of integrated non-destructive surveys for the diagnosis of the materials and for the analysis of the underground structures of an historical building. The studied structure was built in the center of Cagliari, Italy. A single channel 200 MHz Ground Penetrating Radar (GPR) survey was carried out in order to provide the 3D reconstruction of the buried structures localized under the floor level of two rooms of the structure. Two 3D models of the underground environments were derived from orthogonal radar profiles. In addition, active Infrared Thermography (IRT) and Multispectral Imaging techniques (MSI) were utilized to perform the non-invasive inspection of the conditions of the surface materials. IRT images were processed via the Principal Component Analysis (PCA) technique. The reflective patterns of the GPR maps allowed to locate several buried anomalies. IRT data and MSI images have provided a fundamental support to enhance discontinuities and defects of the investigated surfaces.