238 DESTEUCTION OF THE GEEEK EMPIEE by the sea they were built close to the water's edge. In the course of centuries the Golden Horn had silted up a deposit of mud which even before 1453 formed a foreshore outside the north walls of a sufficient extent to have allowed Cantacuzenus to open a foss from Seraglio Point to Aivan Serai, formerly known as Cynegion. The side of the triangle most open to attack was that which faced the land and extended from the Horn to the Marmora. The walls on this landward side, constructed mainly during the reign of Theodosius the Second, had proved themselves during a period of a thousand years sufficiently strong to have enabled the citizens successfully to resist upwards of twenty sieges, and previous to the introduction of cannon were justly regarded as invulnerable. 1 The landward walls are four miles long. From the Marmora to a point where the land has a steep slope for about half a mile down to the Golden Horn, they are triple. The inner and loftiest is about forty feet high and is strengthened by towers sixty feet high along its whole length and distant from each other usually about one hundred and eighty feet. Outside this wall is a second, about twenty-five feet high, with towers similar to though smaller than those along the inner wall. This wall alone is of a strength that in any other mediaeval city would have been considered efficient. Between these two walls was the Peribolos or enclosure, which, though of varying width, is usually between fifty and sixty feet broad. Outside the second was yet another wall, which was a continuation in height of the scarp or inner wall of the ditch or foss and which may conveniently be called a breastwork. This breastwork, like the other two, was crenellated. Though, from the fact that it has been easier of access than either of the others, the summit has mostly perished, some portions of it are still complete. It is important, however, to note that the third wall or breast- 1 In 1204 the Venetians and Crusaders under Dandolo and Monferrat entered the ci ty by capturing the western portion of the walls on the side of the Horn.
