The Mamertine Prison — or Tullianum — was a prison (carcer) located in the Forum Romanum in Ancient Rome

Ancient Rome

Ancient Rome was a thriving civilization that grew on the Italian Peninsula as early as the 8th century BC. Located along the Mediterranean Sea and centered on the city of Rome, it expanded to one of the largest empires in the ancient world....

. It was located on the northeastern slope of the Capitoline Hill

Capitoline Hill

The Capitoline Hill , between the Forum and the Campus Martius, is one of the seven hills of Rome. It was the citadel of the earliest Romans. By the 16th century, Capitolinus had become Capitolino in Italian, with the alternative Campidoglio stemming from Capitolium. The English word capitol...

, facing the Curia

Curia

A curia in early Roman times was a subdivision of the people, i.e. more or less a tribe, and with a metonymy it came to mean also the meeting place where the tribe discussed its affairs...

 and the imperial fora of Nerva

Nerva

Nerva , was Roman Emperor from 96 to 98. Nerva became Emperor at the age of sixty-five, after a lifetime of imperial service under Nero and the rulers of the Flavian dynasty. Under Nero, he was a member of the imperial entourage and played a vital part in exposing the Pisonian conspiracy of 65...

, Vespasian

Vespasian

Vespasian , was Roman Emperor from 69 AD to 79 AD. Vespasian was the founder of the Flavian dynasty, which ruled the Empire for a quarter century. Vespasian was descended from a family of equestrians, who rose into the senatorial rank under the Emperors of the Julio-Claudian dynasty...

, and Augustus

Augustus

Augustus ;23 September 63 BC – 19 August AD 14) is considered the first emperor of the Roman Empire, which he ruled alone from 27 BC until his death in 14 AD.The dates of his rule are contemporary dates; Augustus lived under two calendars, the Roman Republican until 45 BC, and the Julian...

. Located between it and the Tabularium

Tabularium

The Tabularium was the official records office of ancient Rome, and also housed the offices of many city officials. Situated within the Roman Forum, it was on the front slope of the Capitoline Hill, below the Temple of Jupiter Optimus Maximus, to the southeast of the Arx and Tarpeian Rock.Within...

 (record house) was a flight of stairs leading to the Arx of the Capitoline known as the Gemonian stairs

Gemonian stairs

The Gemonian Stairs were a flight of steps located in the ancient city of Rome. Nicknamed the Stairs of Mourning, the stairs are infamous in Roman history as a place of execution.- Location :...

.

The church of San Giuseppe dei Falegnami

San Giuseppe dei Falegnami

San Giuseppe dei Falegnami is a Roman Catholic church in Rome, Italy. Located in the Forum Romanum, the church dates to 1540 and is dedicated to Saint Joseph....

 now stands above the Mamertine.
The origins of the prison's names are uncertain.