As the most important military events in the history of the siege of Constantinople took place in the valley of the Lycus, between the Top Capou on the south and the Adrianople Gate on the north of the valley, it is desirable that the configuration of the locality should be noted carefully. Each of these gates is upon the summit of a hill, the Adrianople Gate indeed being the highest point in the city and, as such, having had near it, as is the almost invariable rule in lands occupied by Greeks, a church dedicated to St. George, who took the place of Apollo when the empire became Christian.[242] Between the two gates exists a valley, about a hundred feet below their level, which is drained by a small stream called the Lycus. The distance between the two gates is seven eighths of a mile. The double walls of Theodosius connect them, while in front of the Outer Wall was an enclosure with the usual breastwork forming the side of the foss. The Lycus enters below these walls through a well-constructed passage still in existence, and flows through the city until it empties itself into the Marmora at Vlanga Bostan. The tower beneath which it has been led is halfway between the Adrianople Gate and Top Capou. About two hundred yards to the north of this tower is the Fifth Military Gate or Pempton, spoken of sometimes by the Byzantines as the Gate of St. Kyriakè, from a church within the city which was close to it, called the Romanus Gate by the writers on the siege, and on old Turkish maps described as Hedjoum Capou or the Gate of the Assault.[243] The foss has a number of dams at irregular distances down each side of the valley. In its lowest part no dams were necessary.[244] The walls between Top Capou and the Adrianople Gate were known as the Mesoteichion, and the name seems to have been applied also to the whole of the valley. The portion of the walls on either side of the Adrianople Gate, or perhaps those only on the high ground to the north of it, was known as the Myriandrion--a name which was applied occasionally to the Gate itself. From a tower to which Leonard gives the name Bactatinian, near where the Lycus entered the city, to Top Capou, the walls were described as the Bachaturean. [Illustration: APPROXIMATE RESTORATION OF THE LAND WALLS OF THEODOSIUS THE SECOND BETWEEN THE GOLDEN AND SECOND MILITARY GATES.] [Illustration: This photograph shows the present condition of a portion of the Landward Walls. They remain for the most part in an equally good state of preservation. The Inner and the Second, usually called the Outer, Wall and the Foss (now without water) are clearly shown. The Third Wall or Breastwork has lost its upper portion and its crenelations, except in a few places. The photograph is reproduced from one by M. Irenian, of Constantinople.]