The Vatican began to be the official mausoleum of the Popes with Leo I. in 461. The place selected is not the interior of the church, but the vestibule, and more exactly the space between the middle doorway (the _Porta argentea_) and the southwest corner, occupied by the _secretarium_, or sacristy, a hall of basilican shape in which the Popes donned their official robes before entering the church. The place can be easily identified by comparing the accompanying reproduction of Ciampini's drawing of the front of the old basilica of S. Peter's with the plan published in chapter iii., p. 127. For nearly two and a half centuries they were laid side by side, until every inch of space was occupied, the graves being under the floor, and marked by a plain slab inscribed with a few Latin distichs of semi-barbaric style. These short biographical poems have been transmitted to us, with a few exceptions, by the pilgrims of the seventh and ninth centuries, whose copies were afterwards collected in volumes, the most important of which is known as the Codex of Lauresheim. At the time of Gregory the Great there was but a small space left near the secretarium. This was occupied by Pelasgius I., Johannes III., Benedict I., and a few others. [Illustration: The Atrium of Old S. Peter's.] Sergius I. (687-701) was the first who dared to cross the threshold of the church, which he did, however, not for his own benefit, but to do honor to the memory of Leo I. The inscription in which he describes the event is too prolix to be given here. It tells us that the grave of Leo the Great was in the vestibule below the sacristy. There he lay "like the keeper of the temple, like a shepherd watching his flock." But other graves had crowded the place so that it was almost impossible to single them out, and read their epitaphs. Sergius therefore ordered the body of his predecessor to be removed to an oratory, or chapel, in the south transept of the church, and to be enclosed in a beautiful monument which he adorned with costly marbles, and with mosaics representing prophets and saints. The monument was destroyed by Paul V. on Saturday, May 26, 1607.