The S. Domenico housing block is situated in a sector of the old city which is of particular interest due to the presence of Roman stratigraphy and of a building belonging to the 16th century monastery attached to the church of S. Domenico. The archaeological investigation, covering an area of circa 250 m2, took place during restructuring work involving the construction of underground garages. Between the end of the 1st and beginning of the 2nd century A.D. a domus was built on this site, of which several walls and a large part of a black and white mosaic floor belonging to a reception room, with geometric and floral motifs, were uncovered. Very little of the adjoining rooms was preserved. The northern side of the domus faced onto an open area, perhaps a courtyard, with a well. In the late imperial period the room with the mosaic was restructured and enlarged, and an _opus signinum_ floor was laid. Between the late antique and early medieval period the area was abandoned and substantial evidence of fires and robbing was uncovered. In the courtyard, where the well was still in use, a building was constructed with reused materials. Between the 6th and 9th century a man and a child were buried in two earth graves which were heavily damaged by successive construction phases. Segments of cobblestone walls and postholes attest an occupation phase preceding the substantial structures erected between the 14th and 18th century for the foundations of the western part of the cloister. These crossed the area from north to south and destroyed a large part of the mosaic floor. Lastly, in 1701 a large tank for slaked lime production cut into a large area of the mosaic. This was later covered by dumped earth when the area became an internal garden, with a small brick built cistern for collecting rainwater. Due to the importance of the archaeological structures, the original building project has been modified and it is planned to open the archaeological context to the public.