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.