When the Emperor Constantine, after his conversion to Christianity, determined to build a basilica in honor of St. Peter, he planned to erect the edifice so that its centre should rise directly over the tomb of St. Peter, who, according to historical documents, was buried not far from the scene of his martyrdom. To do this, he found himself obliged to build so near the Circus of Caligula and Nero that the southern wall of his edifice corresponded exactly to the northern wall of the Circus. He therefore used this wall of the Circus as the southern foundation wall of his church. This naturally brought the southern side of the old St. Peter’s within a very short distance of the _spina_ of the Circus, on which stood the obelisk, with a chapel before it called the Chapel of the Crucifixion. The Chapel disappeared seven or eight centuries ago, but not before its true significance had been quite forgotten, and men supposed the name to refer not to the crucifixion of St. Peter but to the Crucifixion of Our Lord. An old engraving by Bonanni, antedating the reign of Sixtus V, shows the old Church of St. Peter on its southern side, with the obelisk, still tipped by its Pagan ball, standing in close proximity. When the plan for the new Church of St. Peter was accepted it was seen that the southern side of the great edifice would extend so far beyond the limits of the original church that it must entirely cover the spot on which the obelisk was standing; and as the connection of the obelisk with the martyrdom of St. Peter had long since been forgotten, Pope Sixtus V conceived the idea of moving the obelisk to a more conspicuous and important position. Thus it came about that the obelisk now forms the central feature in the piazza before the Cathedral of Christendom; while the place of St. Peter’s crucifixion, that site of transcendent interest to all Christians, remains unidentified, buried beneath the masses of masonry composing the Baptistery on the southern side of the vast structure which bears St. Peter’s name. SCOSSA CAVALLI [Illustration] SCOSSA CAVALLI