The Fortress of The Seven Towers (Turkish: Yedikule) was built during an expansion of the city in the time of the Eastern Roman Empire. The construction first began in the 5th Century C.E. and the walls were knocked down and restored many times in the course of history. The total length of the Yedikule walls is 22 kilometers.
The walls take their name from the seven towers built above them. Four of the towers were built by the Byzantines. The other three were built by Mehmet the Conqueror.
As well as being used for defense, structures in the walls were also employed as a place to guard the imperial treasury, a prison, and a site of execution.