The location of this fortified outpost could not have been more judiciously selected. It commanded the roads from Ostia, Laurentum, and Ardea, those, namely, from which the pirates could most easily approach the city. It commanded also the water-way by the Tiber, and the towpaths on each of its banks. It is a great pity that no stone of this historical wall should be left standing. It saved the city from further invasions of the African pirates, as the _agger_ of Servius Tullius had saved it, centuries before, from the attacks of the Carthaginians. I have examined the ground between S. Paul's, the Fosso di Grotta Perfetta, the Vigna de Merode, at the back of the apse, and the banks of the river, without finding a trace of the fortification. I believe, however, that the wall which encloses the garden of the monastery on the south side runs on the same line with John's defences, and rests on their foundations. We must not wonder at the disappearance of Johannipolis, when we have proofs that even the quadri-portico, by which the basilica was entered from the riverside, has been allowed to disappear through the negligence and slovenliness of the monks. Pope Leo I. erected in the centre of the quadri-portico a fountain crowned by a Bacchic Kantharos, and wrote on its epistyle a brilliant epigram, inviting the faithful to purify themselves bodily and spiritually, before presenting themselves to the apostle within. When Cola di Rienzo visited the spot, towards the middle of the fourteenth century, the monument was still in good condition. He calls it "the vase of waters (_cantharus aquarum_), before the main entrance (of the church) of the blessed Paul." One century later the whole structure had become a heap of ruins. Fra Giocondo da Verona looked in vain for the inscription of Leo I.; he could only find a fragment "lying among the nettles and thorns" (_inter orticas et spineta_). The same indifference was shown towards the edifices by which the basilica was surrounded. They fell, or were overthrown, one by one. In 1633, when Giovanni Severano wrote his book on the Seven Churches, only one bit of ruins could be identified, the door and apse of the church of S. Stephen, to which a powerful convent had once been attached. Stranger still is the total destruction of the portico, two thousand yards long, which connected the city gate--the Porta Ostiensis--with the basilica. This portico was supported by marble columns, one thousand at least, and its roof was covered with sheets of lead. Halfway between the gate and S. Paul's, it was intersected by a church, dedicated to an Egyptian martyr, S. Menna. The church of S. Menna, the portico, its thousand columns, even its foundation walls, have been totally destroyed. A document discovered by Armellini in the archives of the Vatican says that some faint traces of the building (_vestigia et parietes_) could be still recognized in the time of Urban VI. This is the last mention made by an eye-witness.