Opening hours Open daily from 9:00 to 19:00.
Ticket prices Entry is technically free but there is a box at door for donations. It's usually attended by a stern nun, so making at least a token payment is more or less unavoidable.
At the northwest corner of the forums is the Mamertine prison, also known as the Tullianum. This small, dank cell, now forming the basement of the church of San Pietro in Carcere, housed numerous prisoners of the empire including vanquished kings Vercingetorix and Jugurtha and, according to the church, Saints Peter and Paul.
Prisoners were dropped into the cell through a hole in the ceiling, but modern visitors have the use of a flight of stone steps. And while the prisoners were likely to find themselves garotted and dumped in the sewers, the modern exit is by way of a giftshop.
The dramatic cell of the Mamertine Prison
Things to See
The first room you enter has a plaque listing the various martyrs to have suffered in the Mamertine Prison, along with the names of the emperors at the time.
Down a short flight of steps, and just visible through a grating in the floor of the upper room, is the prison itself, an unpleasant and cramped room with a low ceiling.
Here you can see the bars to which St Peter is said to have been chained, and a pool of water in which he is said to have baptised visitors. A small altar bears the inverted cross, a symbol of St Peter which refers to his crucifixion: he asked to be crucified upside down, so that he would not seem to be emulating Christ.
Visiting the Mamertine Prison
The Mamertine Prison is at the north-west corner of the forum, at the bottom of a long flight of steps leading up to the Piazza del Campidoglio.