From the Tullianum or Prison of St. Peter, we were led through a tortuous subterranean passage of Etruscan character, a hundred yards long, cut out of the rock. It was so low that we had to stoop all the way, and in some places almost to creep, and so narrow that a very stout person would have some difficulty in forcing himself through. The floor was here and there wet with the overflowing of neighbouring drains, which exhaled a noisome smell; and we had to pick our steps carefully through thick greasy mud, which on the slopes was very slippery and disagreeable. We followed each other in Indian file, stooping low, each with a wax taper burning dimly in the damp atmosphere, and presenting a most picturesque appearance. This passage was discovered only a few years ago. Numerous passages of a similar nature are said to penetrate the volcanic rock on which the Capitol stands, in every direction, like the galleries of an ant's nest. Some of these have been exposed, and others walled up. They connect the Prison with the _Cloaca_, and doubtless furnished means by which the bodies of criminals who had been executed might be secretly disposed of. The passage in question brought us to four other chambers, each darker and more dismal than the other, and partially filled with heaps of rubbish and masses of stone that had fallen from their roofs and sides. At the top of each vault there was a man-hole for letting a prisoner down with cords into it. A visit to these six vaults of the Mamertine Prison gives one an idea that can never be forgotten of the cruelty and tyranny which underlay all the gorgeous despotism of Rome, alike in the kingly, republican, and imperial periods. Some of the remains may still be seen of the _Scalae Gemoniae_, the "steps of sighs," down which the bodies of those who were executed were thrown, to be exposed to the insults of the populace. The only circumstance that relieves the intolerable gloom of the associations of the Prison is, that Naevius is said to have written two of his plays while he was confined in it for his attacks on the aristocracy; a circumstance which links it to the Tower of London, which has also its literary reminiscences. After having been immured so long in such disagreeable physical darkness--appropriate emblem of the deeds of horror committed in it--we were truly glad to catch at last a faint glimmer of daylight shimmering into the uppermost passage, and to emerge into the open sunshine, from beneath a house at the farther end of the Vicolo del Ghettarello.