The Mamertine Prison (Italian: Carcere Mamertino), in antiquity the Tullianum, was a prison (carcer) with a dungeon (oubliette) located in the Comitium in ancient Rome. It is said to have been built in the 7th century BC and was situated on the northeastern slope of the Capitoline Hill, facing the Curia and the imperial fora of Nerva, Vespasian, and Augustus. Located between it and the Tabularium (record house) was a flight of stairs leading to the Arx of the Capitoline known as the Gemonian stairs.

Christian significance

It is not known when the prison went out of service permanently, but the site has been used for Christian worship since medieval times, and is currently occupied by two superimposed churches: S. Giuseppe dei Falegnami (upper) and S. Pietro in Carcere (lower). The Cross on the altar in the lower chapel is upside down, since according to tradition Saint Peter was crucified that way. It has been long referenced that St. Peter was imprisoned at the Tullianum, and that the spring in the bottom of the pit came into existence miraculously to enable him to conduct baptisms, but the Catholic Encyclopedia points out that the spring had existed long before, and that there is little first hand account of St. Peter's imprisonment there other than being the only single celled prison available for VIPs deemed threats to the state. Saint Paul's imprisonment is well referenced by his Roman citizenship and decree of execution by Nero.[19]

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