The Mamertine Prison, a dingy complex of cells which now lies beneath a Renaissance church, has long been venerated as the place where the apostle was shackled before he was killed on the spot on which the Vatican now stands.
It been a place of Christian worship since medieval times, but after months of excavations, Italian archaeologists have found frescoes and other evidence which indicate that it was associated with St Peter as early as the 7th century.
Dr Patrizia Fortini, of Rome’s department of archaeology for Rome, said: “It was converted from being a prison into a focus of cult-like worship of St Peter by the 7th century at the latest, maybe earlier.
“It was a very rapid transformation. We think that by the 8th century, it was being used as a church. It would have been wonderful to find a document with his [St Peter’s] name on it, but of course that was always going to be extremely unlikely.”
St Peter and St Paul are said to have been incarcerated in the jail by the Emperor Nero.
The two apostles are said to have caused an underground spring to miraculously rise up from the ground so that they could baptise their guards and their fellow prisoners.