The geophysical surveys carried out in 2020 on the site of the Great Constantinian Baths had the aim of obtaining a preliminary knowledge of the subsoil in areas not yet excavated, in order to orient future research. An aero-photogrammetric survey using RPA extended to the entire area of the Constantinian building was integrated with a 3D GPR survey on the two sectors to the east (Area 1) and west (Area 2) of the frigidarium (3,152 and 3,677 m2 respectively). The 3D georadar system employed was equipped with 9 shielded antennas with a frequency of 400MHz and had an exploration depth within 3 m from the ground level. The survey was carried out by the company Esplora S.r.l., a spin-off of the University of Trieste (Roberta Zambrini, Davide Martinucci, Simone Pillon, Giulia Casagrande, Arianna Mocnik).

The area to the east of the frigidarium shows many anomalies that are relatively well legible and attributable to surfaces (floors or preparations) or wall-trenches (of foundation / spoliation). All the anomalies have the orientation of the structures already brought to light and therefore they most likely belong to the thermal building.

The most interesting novelty concerns the organization of the part to the east of the frigidarium, where the presumed rectangular natatio is perhaps to be replaced with a large semicircular pool (diameter: about 31-32 m), as in the “Terme Erculee” in Milan and in the “Kaiserthermen” in Trier. Even the hypothesis of the two courtyards on either side of the natatio is perhaps no longer valid, at least in the first phase of the building.

In area 2, west of the apse of the caldarium, the anomalies are more confused, irregularly shaped, and relatively small, probably because here the stratification is much thicker, the suspensurae are broken through by large blocks of collapsed vault and probably the foundations of the heated rooms are immersed in the groundwater.