There is an upper chamber in the Mamertine prisons, over what is said to have been—and very possibly may have been—the dungeon of St. Peter. This chamber is now fitted up as an oratory, dedicated to that saint; and it lives, as a distinct and separate place, in my recollection, too. It is very small and low-roofed; and the dread and gloom of the ponderous, obdurate old prison are on it, as if they had come up in a dark mist through the floor. Hanging on the walls, among the clustered votive offerings, are objects, at once strangely in keeping, and strangely at variance, with the place—rusty daggers, knives, pistols, clubs, divers instruments of violence and murder, brought here, fresh from use, and hung up to propitiate offended Heaven: as if the blood upon them would drain off in consecrated air, and have no voice to cry with. It is all so silent and so close, and tomb-like; and the dungeons below are so black and stealthy, and stagnant, and naked; that this little dark spot becomes a dream within a dream: and in the vision of great churches which come rolling past me like a sea, it is a small wave by itself, that melts into no other wave, and does not flow on with the rest. It is an awful thing to think of the enormous caverns that are entered from some Roman churches, and undermine the city. Many churches have crypts and subterranean chapels of great size, which, in the ancient time, were baths, and secret chambers of temples, and what not: but I do not speak of them. Beneath the church of St. Giovanni and St. Paolo, there are the jaws of a terrific range of caverns, hewn out of the rock, and said to have another outlet underneath the Coliseum—tremendous darknesses of vast extent, half-buried in the earth and unexplorable, where the dull torches, flashed by the attendants, glimmer down long ranges of distant vaults branching to the right and left, like streets in a city of the dead; and show the cold damp stealing down the walls, drip-drop, drip-drop, to join the pools of water that lie here and there, and never saw, or never will see, one ray of the sun. Some accounts make these the prisons of the wild beasts destined for the amphitheatre; some the prisons of the condemned gladiators; some, both. But the legend most appalling to the fancy is, that in the upper range (for there are two stories of these caves) the Early Christians destined to be eaten at the Coliseum Shows, heard the wild beasts, hungry for them, roaring down below; until, upon the night and solitude of their captivity, there burst the sudden noon and life of the vast theatre crowded to the parapet, and of these, their dreaded neighbours, bounding in!