This occupies the first floor of the structure with stands over the entrance arch of the Porta S. Sebastiano, connecting the tower massive side towers; here there are six panels about the ancient section, dedicated partly to Pomerio (the sacred area inside the city of Rome) and the oldest walls to encircle the ancient city in the VIth and IVth centuries BC. The other panels concern the Aurelian Walls, narrating the historical and political events which determined their construction, and the strategic reasons behind the path of the circuit. They additionally describe the building techniques used in their construction, the gate types, and the transformations and restorations carried out in subsequent IVth, Vth and VIth centuries. The last panel is dedicated to the machines of war used during sieges, both by defenders on top of the walls and the attackers below.
Along the walls are displayed plaster models of the crosses that were cut above the arches of several of the gates in the circuit, or made of brick in various sections of the wall’s path, just like the decorations of palms and sunrays: all of these date to the early Vth century AD, when the height of the walls was doubled. High up on the southern part remain the travertine shelves through which passed the ropes for manoeuvring the portcullis, which ran through a slit in the floor, which still exists, covered over with glass, and descended to close the gate. On the floor in the centre of the room is a black and white mosaic, showing a general on horseback surrounded by soldiers and weapons, which also dates from the early 1940s.