The history of the famous basilica is as follows. Lanciani writes how “wonder has been manifested at the behaviour of Constantine the Great towards S. Paul, whose basilica at the second milestone of the Via Ostiensis appears like a pigmy structure in comparison with that which he erected over the tomb of S. Peter. Constantine had no intention of placing S. Paul in an inferior rank, or of showing less honour to his memory.” In his original design which he carried out, the high road to Ostia ran close by the grave; thus the space at his disposal was limited. But before the fourth century had run out it was imperatively felt that the Church of S. Paul ought to be equal in size and beauty to that on the Vatican Hill: so, in rebuilding the basilica the original plan was changed by the Emperor Valentinian II., in A.D. 386. The tomb and the altar above it were left undisturbed, a great arch was raised above the altar, and westwards from that point, in the direction of the Tiber, a vast church was built. The great work was continued by Theodosius and completed by Honorius, and the splendid decorative work finally carried out by Honorius’ sister, the famous Placidia, who died in A.D. 450. Certain Popes, notably Gregory the Great, and later Honorius III, in A.D. 1226, added to the decorations of Placidia. There was evidently in very early times a cemetery around the crypt which contained the body of S. Paul; this was the original Cemetery of Lucina. But it has been disturbed by the subsequent erection of the Basilica of Constantine, and later by the far larger church begun under Valentinian II. It is hoped that a future careful exploration of the cemetery will bring to light much that is at present unknown. (2) _Cemetery of Commodilla_--is situated on the left of the Via Ostiensis on the road of the Seven Churches. Commodilla was evidently a wealthy Roman lady who, like many other Christians of position and means, gave up her garden to the Christian dead. Nothing, however, is known of her history. Two martyrs, SS. Felix and Adauctus, once well known in Christian story, were interred here. They belong to the time of Diocletian. This Catacomb, apparently of considerable extent, is only very imperfectly known. The Martyrologies mention other “confessors” buried here, but the corridors are either earthed up or are in a state of ruin and confusion, and any thorough investigation would be a costly and difficult piece of work. (3) _Cemetery of S. Thekla._--Nothing is known of the martyr who has given her name to this Catacomb; who must not, however, be confounded with the celebrated saint of the same name who belongs to Lycaonia, and is traditionally connected with S. Paul. This cemetery has been but imperfectly examined as yet; its extent is unknown. THE VIA ARDEATINA