Just north of the Forum in Rome stands San Giuseppe dei Falegnami (St. Joseph’s of the Carpenters), a Roman Catholic church dedicated to Jesus’s foster father, Joseph of Nazareth. Beneath this structure are the remains of the traditional site of the imprisonments of the Apostle Paul and the Apostle Peter in Rome. This prison was simply known as “Carcer” (“prison”) in Paul’s day. The term “Mamertine” was attributed to the prison in the Medieval Period.

The Carcer was the only prison in ancient Rome. When someone was sentenced to death, they were brought here to await execution. Pictured here is the upper chamber of the ancient prison. Though it is now subterranean, this section of the Carcer was once at street level.

Below the upper chamber is a circular room called the Tullianum. This structure may have held religious importance even before the days of the apostles; votive offerings were found during excavations, indicating ceremonial activity from the period before it was linked to the Carcer.

Before the stairs were added, those prisoners who entered the Tullianum from the Carcer were lowered through a hole in the Carcer’s floor. The name “Tullianum” is probably derived from the Latin word for a spring of water, and incidentally, this section of the prison does, in fact, house a well. According to tradition, the apostle Peter caused the well-water to spring up so that he might baptize his jailors, St. Processus and St. Martinianus. It is debated, however, whether Peter was actually incarcerated here.

The state rarely incarcerated common criminals, but kept the Mamertine Prison for political prisoners doomed for execution by being thrown off the Tarpeian Rock. Enemies of the State, such as Jugurtha and Vercingetorix, were often strangled in the Tullianum. A door in the chamber offered access to the Cloaca Maxima (Rome’s sewer system), and it is thought that the bodies of executed prisoners may have been carried out through there.

Because of its association with Paul and Peter, the Mamertine Prison has been used as a place of worship since roughly the 7th century. This chapel, which sits above the Carcer’s upper chamber, was established as a place to house the ornate crucifix which once adorned the structure’s façade.