The Long Wall of Thrace, also called the Anastasian Wall, was a system of fortifications erected west of Constantinople. The remains of walls, which are about 65 km from Constantinople, extended from Selymbria (modern Silivri) to the Black Sea. The Wall is part of the additional defenses for Constantinople constructed during the 5th century AD and probably continued in use until the 7th century. Originally the Wall was around 56 km long, but less than half of the total length now survives above ground. It is best preserved in the rolling woodland of the northern sector where the Wall stands in place up to 4m in height. Associated with the Wall is a well preserved ditch, outerwork, gates and forts. As it survives it is the most monumental linear fortification dating from antiquity in continental Europe, comparable only with Hadrian's Wall in its complexity and preservation. Recent road construction and other developments associated with the expansion of Greater Istanbul are now posing a major threat to the surviving remains.The wall proved ineffective (probably because of its length and the lack of a sufficient garrison to man it) and was many times penetrated by invaders, beginning in 559. According to the preface to novel 26 of Justinian I, there were two vicarii of the Long Walls: one for military affairs, the other for civil administration. In later centuries the commander responsible for the defense of the wall was the Komes ton Teicheon.