This is the name given from the Middle Agesto the ancient State Prison called Tullianum. The place is bound to the memory of St. Peter and Paul, but the tradition for them to be imprisoned here for nine months before escaping due to the jailers’ conversion seems to be without any foundation. The current travertine facade that covers the more ancient one made of tuff blocks presents a large inscription that bears the names of the consuls C. Vibius Rufinus and M. Cocceius Nerva. Internally a trapezoidal room communicates with a circular room below through a hole in the floor - that is no longer used and replaced by a modern ladder. This is really a terrifying place where the State prisoners were first confined and then strangled: this was the fate that was reserved among many others to Jugurtha and Vercingetorix. Regarded as sacred from the 15th century, the Mamertine Prison was consecrated to S. Peter in Carcere.