The excavation investigated a small part of the area of the northern aulae of the baths of Diocletian, by the north palestra. A series of foundation structures were uncovered, abutting each other in a sequence that was difficult to interpret. The earliest structure was probably a small drain paved in bipedales with stamps from the period of Diocletian, part of the water supply network of the baths. It seemed to have been obliterated by a conglomerate foundation poured into formwork, on the same alignment as the baths’ structures. The latter was in turn obliterated by the brick foundations of the aulae, whose walls are partially preserved. At the point in which there was the door between the two aulae, a large block of marble was inserted into the foundations, perhaps the support for a column decorating the doorway and supporting the architrave. The rapid succession of the three phases, all within Diocletian’s reign, suggests a series of variations and changes of mind during the construction of the imperial baths; variations and changes easily explained by the vastness and complexity of the structure that was built.