II. Thus did Justinian fortify this stronghold;[36] he also constructed reservoirs of water between the city walls and the outwork, and very close to the Church of St. Bartholomew the Apostle, on the west side. A river runs from the suburb called Corde, distant about two miles from the city. Upon either side of it rise two exceedingly rugged mountains. Between the slopes of these mountains the river runs as far as the city, and since it flows at the foot of them, it is not possible for an enemy to divert or meddle with its stream, for they cannot force it out of the hollow ground. It is directed into the city in the following manner. The inhabitants have built a great channel leading to the walls, the mouth of which is closed with numerous thick bars of iron, some upright and some placed crosswise, so as to enable the water to enter the city, without injury to the strength of its fortifications. Thus the river enters the city, and after having filled these reservoirs, and been led hither and thither at the pleasure of the inhabitants, passes into another part of the city, where there is an outfall constructed for it in the same way as its entrance. The river in its progress through the flat country made the city in former times easy to be besieged, for it was not difficult for an enemy to encamp there, because water was plentiful. The Emperor Justinian considered this state of things, and tried to find some remedy for it; God, however, assisted him in his difficulty, took the matter into His own hands, and without delay ensured the safety of the city. This took place in the following manner.