What Roman prison in Rome was traditionally where Saints Peter and Paul were held?

What Roman prison in Rome was traditionally where Saints Peter and Paul were held? The answer is Mamertine Prison.

Mamertine Prison was Rome’s ancient state prison, traditionally identified with the Tullianum, beneath the modern church of San Giuseppe dei Falegnami near the Roman Forum. Tradition holds that Saints Peter and Paul were confined there, although the historical evidence for both imprisonments is uneven and the exact locations connected with their custody remain debated.

The prison probably originated in the early Roman period, perhaps during the reign of Ancus Marcius in the 7th century BCE. Its lower chamber was a dark underground cell or oubliette reached through an opening above. Ancient accounts associate the site with the detention and execution of high-profile enemies of Rome, including Jugurtha of Numidia and Vercingetorix.

Carcer Tullianum is not a separate competing answer: it is the ancient name associated with Mamertine Prison. The names “Mamertine” and “Tullianum” are therefore commonly used for the same historic complex. Christian tradition also says Peter baptized his guards using a spring in the lower chamber, though that story is devotional rather than firmly established by contemporary evidence.