At the right-hand end of the latter street is the Apollo Theatre, built on the site of the Tor di Nona prison, where Beatrice Cenci was confined. Passing into the Piazza Ponte S. Angelo, on our left, is the Italian Free Church of Gavazzi, and in the Palazzo Altoviti, in front, lived Visconti. _We turn to the right over_ THE BRIDGE OF S. ANGELO, (_Ponte S. Angelo_,) which is decorated with ten angels standing on the parapet, bearing the instruments of our Lord's passion; and SS. Peter and Paul, an addition made in 1668 by Clement IX. It is the finest bridge in Rome, and was built by Hadrian. TOMB OF HADRIAN, NOW THE CASTLE OF S. ANGELO. (_Castel S. Angelo. Permissions required: see page 353._) It was covered with white Paros marble, and decorated with statues of the gods and heroes, the works of Praxiteles and Lysippus, which were hurled upon the heads of the Goths. Erected by Hadrian, A.D. 130. The porphyry sarcophagus, which is supposed to have contained his remains, is now used as the font in the chapel on the left in S. Peter's. Procopius thus describes it: "The tomb of the Emperor Hadrian is situated outside the Porta Aurelia. It is built of Parian marble, and the blocks fit close to one another without anything to bind them. It has four equal sides, about a stone-throw in length; its altitude rises above the city walls; on the top are statues of the same kind of marble, admirable figures of men and horses." Lucius Verus, Antoninus Pius, Marcus Aurelius, Commodus, were all buried here. It was first turned into a fortress A.D. 423. Popes John XXIII. and Urban VIII. built the covered way connecting it with the Vatican. One of the barrack-rooms contains frescoes by Pierino del Vaga and Sicciolante, another by Giulio Romano. A circular room, surrounded with carved wood cases, once contained the archives of the Vatican. A large iron-bound chest contained the treasury. Some dark cells built in the thickness of the walls are shown as the prisons of Beatrice Cenci (?), Cellini, Cagliostro, and others. Tradition asserts that Gregory the Great saw S. Michael standing over the fortress sheathing his sword as a sign that a pestilence was stayed; to commemorate which the castle is now surmounted by a figure of the archangel in the act of sheathing his sword. This old castle served for a fortress during several ages, and its first cannon were cast out of part of the bronze taken from the roof of the Pantheon. _The Borgo Nuovo leads to_ the Cathedral, passing, _on the right_, the Church of S. Maria, built on the site of a pyramid to Honorius, 423 A.D., which is represented on the doors of S. Peter's. S. PETER'S. (_S. Pietro._) EXTERIOR.