The Mamertine Prison in Rome is the building where the saints Peter and Paul are supposed to have been imprisoned before they managed to escape after having converted their guards to Christianity. The prison is located underneath the Church of San Giuseppe dei Falegnami.
Mamertine Prison Rome
Address, opening hours and admission
The address of the Carcere Mamertino is Clivo Argentario/Via del Tulliano, 00186 Rome, Italy. Rione: Campitelli. Metro: Colosseo. The Mamertine Prison is opened from 09.00 until 19.00 hours (in winter only till 17.00 hours). Admission is 10 Euros. Children below the age of 10 do not pay. The OMNIA Vatican & Rome Card is valid.
History

The Mamerine Prison was built in the 7th century BC and is thus the oldest prison in Rome. Construction was ordered by the 4th king of Rome, Ancus Martius. Until the Middle Ages this ancient state prison was called Tullianum.
Initially its function was probably that of a cistern for water that came from a small well in the floor.
Generally prisoners were not held here for very long periods. Either they were executed or after some time simply starved to death.
According to legend Saint Peter stumbled on his way down into the prison, thereby supposedly leaving an imprint of his head in the wall.
The two saints, who were locked up in the dark, managed to conjure up some water. The guards Processo and Martiniano were so impressed that they converted immediately and let their prisoners escape. The Latin word for “puddle of water” is tullus, which is why the prison came to be called Tullianum.
Other VIPs that spent time in the Mamertine Prison were the King of Numidia and the Gallic leader Vercingetourix, who had tried to lead his people into a revolt against Caesar (52 BC).
In the 15th century the prison came to be considered a holy building. It is dedicated to San Pietro in Carcere (“Saint Peter in Prison”).
Description
The present marble façade dates back to the year 40 BC and covers the original tuff stone one, which was made two centuries earlier. An inscription shows the names of two consuls, C. Vibius Rufinus and M. Cocceius Nerva.
The entrance opens up into a trapezoid space, which is called the carcer. Underneath this space is a round room, which is the actual Tullianum. Until not too long ago this space could only be entered through a hole in the floor, but nowadays there are steps leading down. The hole itself is now covered with an iron gate.
There might have been a smaller entrance in the right wall. This was located above the present street level and is now bricked up. At the time there were other rooms called Lautumiae, which had been dug out in the tuff stone.
There are two plaques on this wall, of which the first one lists its most famous prisoners and how they died. The other one names the imprisoned martyrs and saints and who their persecutors were.
An iron door at the back of the Tullianum probably led to the sewer system, which was called Cloaca Maxima. It is possible that this was used to get rid of the dead bodies, which then floated through the sewers to end up in the river Tiber.
An altar with the busts of Saints Peter and Paul is placed against the back wall.