The great piers are 253 feet in circumference; which space is exactly occupied by the church and house of S. Carlo, in the Via Quattro Fontane. Near the first pier of the right side is the celebrated bronze seated statue of S. Peter, with the keys in one hand, the other raised in the act of blessing, under a canopy erected by Pius IX., whose portrait in mosaic surmounts it. It is asserted by some that this was a statue of Jupiter, supremely good and great, that stood in the Capitoline temple, and that it was altered into S. Peter; others say they recast Jupiter into the "Jew Peter." THE SACRISTY is connected with S. Peter's by a long gallery, and is adorned with pillars, statues, paintings, and mosaics. It is entered by passing through a door under the monument to Pius VIII., in the left aisle. There is a very rich collection of church plate and vestments kept in the _guardaroba_, which visitors should not fail to see. THE CRYPT. _Orders must be obtained of Cardinal Ledockowski, Palazzo Cancelleria. It must be visited before 11 A.M._ The entrance is at the side of the statue of S. Veronica. It contains the tombs of the early Popes, and also some old bas-reliefs, and some very ancient statues of S. Peter. Adrian IV., the only English Pope, is buried here, and also several distinguished historical characters, including "the last of the Stuarts." THE DOME. _Orders must be obtained of Monsignor Fiorani, in the Sacristy, for visiting the dome, which is only open without an order on Thursdays, between 8 and 10 A.M._ It is reached by a winding ascent, the entrance being opposite the Stuart monument. On the platform of the roof the cupolas, domes, and pinnacles are seen to advantage; and hence, by different staircases between the walls of the cupola, the ball is reached. During the ascent, a fine view may be obtained of the lower parts of the church, as well as of the mosaics and stuccoes which embellish the interior of the dome. On reaching the summit, a panoramic view of Rome and the Campagna is had, quite repaying the labour of the ascent. THE VATICAN. From the vestibule of S. Peter's we see, to the fullest advantage, the fine piazza, with the Vatican on our left, which presents very much the appearance of a large factory. Having been erected by different architects in various eras, it has no systematic design, and is, in fact, a collection of palaces built by different Popes. The entrance is at the bend of the colonnade. _Permission to visit the_ MUSEUM, GALLERIES, LIBRARY, _&c., must be obtained from Monsignor Macchi, at his office, between the hours of 10 and 1, thus enabling a party of five to pay a visit any day, except Saturdays, Sundays, and festas, between 9 and 3, except the Museum of Statues, which is closed every Thursday, when the Egyptian and Etruscan Museums and the Gallery of Tapestries are only open_. The galleries are gained by THE SCALA REGIA,