The uppermost vault is still below the level of the surrounding soil, and the entrance to it is by the church of San Giuseppe di Falegnami, the patron of the Roman joiners, built over it. Beneath is a subterranean chapel, forming a sort of crypt to the upper church, called San Pietro in Carcere, containing a curious ancient crucifix, an object of great veneration, and hung round with blazing lamps and rusty daggers, pistols, and other deadly instruments, the votive offerings of bandits and assassins who sought at this shrine of the chief of the apostles to make their peace with heaven. Descending from the chapel by a flight of steps we come through a modern door, opened through the wall for the convenience of the pilgrims who annually visit the sacred spot in crowds, to the ancient vestibule, or grand chamber of the prison, commonly called the Prison of St. Peter from the church tradition which asserts that the great apostle was confined here by order of Nero before his martyrdom. The pillar to which he was bound is still pointed out in the cell; and Dr. Parker, lifting up its cover, showed us a well in the pavement of the floor, which is said to have sprung up miraculously to furnish water for the baptism of the jailors Processus and Martinianus whom he had converted, though, unfortunately for this tradition, the fountain is described by Plutarch as existing in the time of Jugurtha's imprisonment. Indeed there is every reason to believe that this chamber was originally a well-house or a subterranean cistern for collecting water at the foot of the Capitol, from which circumstance it derived its name of Tullianum, from _tullius_, the old Etruscan word for _spring_, and not from Servius Tullius, who was erroneously supposed to have built it. The whole chamber in primitive times was filled with water, and the hole in the roof was used for drawing it out. Dr. Parker gave us a little of the water in a goblet, but, notwithstanding its sacred reputation, it tasted very much like ordinary water, being very cool and fresh, with a slight medicinal taste. He also pointed our attention to a rugged hollow in the wall of the staircase, and told us that this was the print of St. Peter's head in the hard stone, said to have been produced as he stumbled and fell against it, coming down the stair a chained prisoner. It requires no small amount of devotional credulity to recognise the likeness or to believe the story.