CALIGOLA: a project for enhancing the knowledge of underground archaeological sites in the Palatine Hill through the integration of geological and geophysical data with new technologies

This work illustrates the activities carried out within the CALIGOLA Project, a research program funded by the Lazio Region and MUR (Minister of University and Research) with the goal of improving the set of skills and technologies dedicated to the protection and fruition of Cultural Heritage. Situated at the top the Palatine hill in Rome, the Central Cryptoporticus comprises hypogea structures that are the object of this investigation. They are part of a complex underground archeological site pertaining to the Domus Tiberiana, the first dynastic palace re-built by Nerone after the fire of 64 AD. To address the collapse and subsidence risk affecting the examined area, stabilization measures are necessary. These measures aim to consolidate underground anthropogenic and natural cavities, including water drainage tunnels and voids resulting from the extraction of building materials. In order to enhance our understanding of the geological risks faced by the monument, a 3D geological model of the superficial and shallow subsoil portion of the area, comprising the man-made structures and caves, was created. This model is based on the analysis and elaboration of a large amount of geological data, such as geological cross-sections, geological map and boreholes. Additionally, it incorporates the 3D model of the underground Central Cryptoporticus, obtained through laser scanning, along with geophysical data, such as new Ground Penetrating Radar (GPR) prospections, Electrical Resistivity Tomographies (ERT) and ambient noise measurements carried out during field work in 2023-2024. The 3D model also comprises geophysical and geotechnical data acquired over time on the Palatin hill (Mancini et al., 2014; Moscatelli et al., 2014). This novel methodological approach combines subsoil and laser scanning data for reconstructing precise, realistic, high-resolution, small-scale 3D models, beneficial for studying historically and\or archeological sites. In this case, it aids identifying instability factors concerning the structures and detecting new, unexplored underground cavities. The information derived from the use of velocimetric sensors capable of detecting the three components of motion in a wide range of frequencies and with high dynamics enrich this approach. Concepts from dynamic buildings identification have been adapted to characterize the dynamic response of the three excavated sections of the Cryptoporticus. Simultaneously, the digital representation of this Cultural Heritage has facilitated the development of a virtual model and game-based learning experience. This activity addressed a prestigious case study in the direction of disseminating knowledge of mitigation measures aimed at reducing the impact of disasters on Cultural Heritages (Gaudiosi et al., 2022). It may be meant as a new way to encourage the preservation and conservation of historical and archeological sites, aligning with the principles of the Nara declaration (NDWG, 1994).