Between the end of 2000 and the beginning of 2001, at the same time as the restoration of the ex-monastery of S. Teresa dei Maschi in Bari Old Town, the present home of the “De Gemmis” Provincial Library, trenches were dug in Strada Lamberti prior to the installation of cabins for underground utilities necessary to the functioning of the building. At a depth of 0.50 m below the monastery floor excavation revealed a series of substantial walls running parallel to the façade (Strada Lamberti). Widening of the investigation to the road showed how these walls constituted an interesting example of horizontally stratified walls, a first for Bari. The examination of the walls and their particular layout in plan suggested that this was the frontage of a medieval insula, which was uncovered for a total of 12.50 m and had a uniform width of 0.60 m. The construction of the imposing convent of the Barefoot Carmelites at the end of the 17th century obviously led to the demolition of the medieval structures, of which some of the springing of the vaults were preserved on a residual wall at a height of between 1 and 2 m. On the basis of some well dated finds it was possible to attribute the insula to the middle centuries of the Medieval period. In this sense certain dating was provided by a sculptural element probably from a pluteus stylistically datable to the 9th-10th century, reused in the foundation of a tomb containing an infant burial, which had been desecrated, abutting the southern part of the wall. Two bronze belt buckles, similar to those found in late medieval Apulian contexts, were also recovered from a tomb, abutting the stretch of wall further north. The last stretch of wall with semi-piers placed like pilasters and a refined facing can also be referred to this chronological horizon. Built in light coloured limestone ashlar blocks, well squared and set onto perfectly horizontal courses, the technique used in the structure was the same as that of the main Roman and late Roman buildings in central-northern Apulia. The archaeological investigation also undertaken along the monastery’s southern frontage (Strada S. Teresa dei Maschi) at the same time as restoration work, produced equally important results. In this sector the excavation uncovered the remains of a room, the layout of which suggested it belonged to the southern part of a tower-house. It was 2.62 m wide and preserved to a height of 2.30 m, at its extremities were two short stretches of wall, of the same width, whose orthogonal development towards the north was cut by the perimeter structures of the late 17th century monastery. The building typology of this unusual structure with both defensive and residential functions has many parallels in Bari Old Town, both in written documents and in the numerous constructions that still stand today in the proximity of the archaeological area of S. Teresa dei Maschi.