The Crucifixion of Peter and Paul

The maritime prison is located very close to the forum. The Romans didn't really have prisons. They had places where they would hold people before trial, but putting people in jail was not a regular punishment for the Romans. So this is where Peter and Paul were both held. And I think it was a church or maybe a church still technically where they occasionally hold services there. On the altar, there's an upside down cross.