This conclusion is again in harmony with the figures of Zosimus and the Notitia, which, it will be remembered, brought the line of the Constantinian Wall close to this point.
(f) The Cistern of Bonus, the next landmark to be considered, was built by the Patrician Bonus, celebrated in Byzantine history for his brave defence of the capital in 627 against the Avars and the Persians, while the Emperor Heraclius was in Persia carrying war into the enemy’s country.[[81]]
Where this cistern was situated is a matter of dispute which cannot be definitely settled in our present state of knowledge. Gyllius identified it with a large cistern, three hundred paces in length, which he found robbed of its roof and columns, and turned into a vegetable garden, near the ruins of the Church of St. John in Petra, on the Sixth Hill.[[82]] The cistern has disappeared since that traveller’s day, but as the Wall of Constantine never extended so far west, the identification cannot be correct.
In Dr. Mordtmann’s opinion, the Cistern of Bonus was the large open reservoir to the south-west of the Mosque of Sultan Selim, on the Fifth Hill,[[83]] and there is much to be said in favour of this view.
The Cistern of Bonus was, in the first place, situated in one of the coolest quarters of the city, and beside it, on that account, the Emperor Romanus I. erected a palace,[[84]] styled the New Palace of Bonus,[[85]] as a residence during the hot season. Nowhere in Constantinople could a cooler spot be found in summer than the terrace upon which the Mosque of Sultan Selim stands, not to speak of the attractions offered by the superb view of the Golden Horn from that point. Furthermore, the Cistern of Bonus was within a short distance from the Church of the Holy Apostles, seeing that on the eve of the annual service celebrated in that church in commemoration of Constantine the Great, the Imperial Court usually repaired to the Palace of Bonus, in order to be within easy riding distance of the sanctuary on the morning of the festival.[[86]] A palace near the reservoir beside the Mosque of Sultan Selim would be conveniently near the Church of the Holy Apostles, to suit the emperor on such an occasion. To these considerations can be added, first, the fact that on the way from the Palace of Bonus to the Church of the Apostles there was an old cistern converted into market gardens,[[87]] which may have been the reservoir near the Mosque of Sultan Selim; and, secondly, the fact that the Wall of Constantine, on its way from the Cistern of Aspar to the Golden Horn passed near the site now occupied by the Mosque of Sultan Selim, and, consequently, close to the old cistern adjoining that mosque. But to this identification there is a fatal objection: the Cistern of Bonus was roofed in,[[88]] whereas the reservoir beside the Mosque of Sultan Selim appears to have always been open.
Dr. Strzygowski has suggested that the Cistern of Bonus stood near Eski Ali Pasha Djamissi,[[89]] on the northern bank of the valley of the Lycus, and to the south-west of the Mosque of Sultan Mehemet.[[90]] No traces of a cistern have been found in that locality, but the conjecture satisfies the requirements of the case so far as the proximity of that site to the line of Constantine’s wall and to the Church of the Holy Apostles is concerned. Why that position should have been selected for a summer palace is, however, not apparent.
We have said that the Constantinian Wall, upon leaving the Cistern of Aspar, turned sharply to the north-east, and made for the shore of the Golden Horn by running obliquely across the ridge of the Fifth Hill.
This view of the case is required, first, in order to keep the breadth of the city within the limits assigned by the Notitia; and, secondly, by the statement of the same authority that the Eleventh Region—the Region at the north-western angle of the Constantinian city—did not extend to the shore of the Golden Horn: “Nulla parte mari sociata est.”[[91]] For this statement implies that the fortifications along the northern front of that Region stood at some distance from the water. But the northern slope of the Fifth Hill is so precipitous, and approaches so close to the Golden Horn that the only available ground for the fortifications on that side of the city would be the plateau of the Fifth Hill, where the large cistern beside the Mosque of Sultan Selim is found.
(g) The church dedicated to the three martyr brothers, SS. Manual, Sabel, and Ishmael, must likewise have been on the Fifth Hill; for it stood where the wall began its descent (κατήρχετο)[[92]] towards the Golden Horn. This agrees with the statement of the Synaxaria that the church was situated beside the land wall of Constantine, upon precipitous ground, and near the Church of St. Elias at the Petrion.[[93]]
(h) As to the district of Harmatius, named after Harmatius, a prominent personage in the reign of Zeno,[[94]] it must be sought in the plain bounded by the Fifth, Fourth, and Third Hills, and the Golden Horn, the plain known in later days as the Plateia, (Πλατεῖα). To that plain the fortifications of Constantine would necessarily descend from the Fifth Hill, in proceeding on their north-eastern course to the Golden Horn; and there also the figures of the Notitia require the northern end of the walls to terminate. Doubtless in the time of Constantine the bay at this point encroached upon the plain more than at present.