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The Mamertine Prison, known in antiquity as the Carcer Tullianum, is the oldest known prison in Rome. It is located on the Clivo Argentario at the northeastern edge of the Roman Forum, beneath the church of San Giuseppe dei Falegnami. According to ancient tradition, the prison was founded in the seventh century BCE during the reign of King Ancus Marcius. It was intended as a secure holding place for enemies of the state who were awaiting execution, rather than as a long-term detention facility.
Ancient authors such as Livy associate the prison’s construction with Rome’s early expansion and the rise of crime within the growing city, particularly around the Aventine Hill. The threat of imprisonment in such a severe space was meant to reinforce public order and demonstrate the authority of the Roman state.
The structure consists of two chambers built into the southern slope of the Capitoline Hill. The lower chamber, known as the Tullianum, is the oldest part of the complex and dates to the Archaic period of the seventh century BCE. It is roughly semicircular in shape and lies deep below ground. Above it is the upper chamber, called the Carcer, which was added in the sixth century BCE. This room has a trapezoidal plan and is constructed from large blocks of red and yellow tuff, originally covered by a barrel vault.
The Tullianum functioned as the prison’s execution chamber. Condemned prisoners were lowered into it through a circular opening in the ceiling and held there until execution, usually by strangulation or decapitation. The historian Sallust described the space as dark, neglected, and foul-smelling, emphasizing its terrifying conditions. The name Tullianum likely derives from the Latin word tullius, meaning a spring, referring to a natural water source that flowed underneath the chamber. A drain carried this water, and the bodies of executed prisoners, into the Cloaca Maxima, Rome’s main sewer.
The prison’s location was highly symbolic. Positioned above the Forum and along the route of Roman triumphs, it played a role in public displays of victory and punishment. Captured enemy leaders were often paraded through the city during triumphal processions and then led into the Carcer to be executed. This final act marked the end of both the victorious general’s command and the defeated enemy’s life. Notable prisoners included Jugurtha, king of Numidia; Vercingetorix, leader of the Gallic resistance to Rome; and Sejanus, praetorian prefect under Emperor Tiberius.
The Mamertine Prison was renovated several times during the Republican period and the early Empire, including the addition of a large travertine façade. It remained in use until at least the fourth century CE.
In Christian tradition, the prison is associated with the imprisonment of the apostles Peter and Paul before their martyrdom under Emperor Nero. Legends claim that a spring miraculously appeared in the prison, allowing Peter to baptize his fellow prisoners, and that Peter struck his head against the wall while descending into the cell, leaving an imprint in the stone. From the early Middle Ages, the site became known as the Mamertine Prison, possibly named after a nearby temple of Mars. Both chambers were converted into Christian chapels, and in the sixteenth century the church of San Giuseppe dei Falegnami was built above the ancient structure.
Today, the remains of the Mamertine Prison can still be visited beneath the church. Accessed by a narrow staircase, the dark and confined chambers preserve the stark atmosphere of one of Rome’s most feared institutions.
Bibliography
- Cadoux, T. J. (2008). The Roman Carcer and Its Adjuncts. Greece & Rome, 55(2), 202–221. http://www.jstor.org/stable/20204210
- Grout, James. “Tullianum.” University of Chicago. https://penelope.uchicago.edu/encyclopaedia_romana/romanforum/tullianum.html
- Larsen, Matthew and Mark Letteney. (2025). Spaces of Incarceration: A Typology of Prisons in Antiquity. In Ancient Mediterranean Incarceration (1st ed., pp. 45–88). University of California Press. https://doi.org/10.2307/jj.30089702.8
- Olson, Mary. (2008). “Philosophies of Imprisonment in Late Antiquity.” Constructing the Past, Vol. 9: Iss. 1, Article 7. https://digitalcommons.iwu.edu/constructing/vol9/iss1/7
- Platner, Samuel. (1929). “Carcer.” In A Topographical Dictionary of Ancient Rome (p.99-100). Retrieved from: https://penelope.uchicago.edu/Thayer/E/Gazetteer/Places/Europe/Italy/Lazio/Roma/Rome/_Texts/PLATOP*/Carcer.html
- Ruyter-Harcourt, Isadora. (2015). “A Dispatch from Rome: The Mamertine Prison.” Columbia University. https://blogs.law.columbia.edu/foucault1313/2015/10/17/the-mamertine-prison-a-dispatch-from-rome/
Carcer: the ancient state prison of Rome, situated between the temple of Concord and the curia at the foot of the Capitol. It was used simply as a place of detention, and not of penal servitude, though executions (i.e. those of Jugurtha and Vercingetorix and of the Catilinarian conspirators) also took place here. The subterranean part was called Tullianum.
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The name (Liv. XXIX.22.10; XXXIV.44.8; Serv. ad Aen. VI.573; Calpurn. Flacc. decl. 4: Acta Chrysanth. et Dariae, 25 Oct. p483) is by Varro (LL V.151) and Festus (356) derived from Servius Tullius, who was the builder of this portion of the carcer: while Livy (I.33) attributes the construction of the carcer to Ancus Martius. Sallust (Cat. 55) describes it in a well-known passage: in carcere locus quod Tullianum appellatur, ubi paullulum ascenderis ad laevam, circa duodecim pedes humi depressus. Eum muniunt undique parietes atque insuper camera lapideis fornicibus iuncta, sed incultu, tenebris, odore foeda atque terribilis eius facies est.
This lower chamber of the buildingb is subterranean and was originally accessible only by a hole in the roof. It is nearly 7 metres in diameter: in the walls only three courses of stone are visible, and it is thus less than 6 feet high: but three more courses may still be hidden by the present floor, and this would give the 12 feet of which Sallust speaks. The building was, according to one theory, in origin a cupola grave, like those of Mycenae: while others think that it served as a water reservoir, and derive the name Tullianum from tullus, a spring. A small spring does indeed still rise in the floor; and the absence of incrustation, used as an argument against the second hypothesis, has little weight, as the water is not calcareous.
It has generally been believed that the cupola was cut by the constructors of the upper chamber; Tenney Frank (TF 39‑47) now supposes, without sufficient reason, that the lower chamber originally had a flat wooden roof, which later served as a scaffolding for the flat stone vault, which dates from after 100 B.C. But the holes to which he points in support of this theory may just as well have been cut for this scaffolding. p100 There is little doubt that the chamber was originally circular (the statement that the straight chord on the side towards the Comitium is of rock, is incorrect). See JRS 1925, 121.
Most authorities attribute to it a high antiquity: but Frank assigns the lower chamber to the third century B.C. owing to the use of peperino (not tufa, as all other authorities state) and the regularity of the blocks, uniformly 56 cm. high: while the date of the drain leading into the forum appears to be debateable.
The upper room is a vaulted trapezoid, the sides varying in length from 5 to 3.60 metres. This Frank assigns to about 100 B.C. on similar grounds; and the vault of the lower chamber, as we have seen, to a slightly later date.
A new façade of travertine was added by C. Vibius Rufinus and M. Cocceius Nerva, consules suffecti, perhaps in 22 A.D. (CIL VI.1539 = 31674; cf. 9005; Pros. I. p428, No. 972; III. p424, No. 395), but, it may be, a good deal later (Mommsen, Westdeutsch. Zeitschr., Korrespondenzblatt, 1888, 58, puts it a little before 45 A.D.; cf. ILS III. p342). It was still used as a prison in 368 A.D. (Amm. Marc. XXVIII.1.57), so that the tradition that it was converted into an oratory in the fourth century is without foundation; and the fons S. Petri, ubi est carcer eius of Eins. (7.2), cannot have been here (Mon. L. I.481; HCh 421‑422).
The name Mamertinus is post-classical.
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Cite this page as: Darius Arya, The American Institute for Roman Culture, Carcer Tullianum (Mamertine Prison),” Ancient Rome Live. Last modified 01/28/2026. https://ancientromelive.org/carcer-tullianum-mamertine-prison
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