During excavations undertaken in July 2001 to connect the Saudi Arabian embassy to the mains gas supply, ancient structures came to light immediately below the road surface in via Vesalio, at less than 10m from the crossroads with Piazza Rio de Janeiro. These comprised the S-W corner of a semi-interred room with plastered walls and a black and white mosaic of rectangles and squares forming a “chequer-board” pattern. Below this room, which can be dated to the mid-Imperial period on the basis of the construction technique and the ceramic finds, were traces of a pre-existing structure comprising a wall in opus reticulatum, on a N-S alignment which formed the western side of a small tank lined in opus signinum. These structures can be dated to between the end of the Republican and the first half of the Imperial period and probably relate to the non-sepulchral part of the building which is known from the excavations of 1888 between via Vesalio and via Saliceto. (Simonetta Di Meo-Daniele Pantano)