What always impresses me with these Roman buildings is their indifference to the limitations placed by the gods on the landscape. The auditorium is not built on a natural slope but is supported by three concentric successive vaulted corridors that increase in height and bear the building. At the end of the performance I asked a servant to show me this marvel of engineering. I followed him through the vomitorium, the middle entrance that gives access to the orchestra from the corridors, and walked around the middle corridor (now used msotly for storage) and the outer one with the twelve windows on the wall that ventilate this main audience passageway. Eventually we exited from the back of the building and saw the two exterior staircases that give access to the the top row of seats.