Ayaz Kale is a group of mud fortresses in Khorezm. The complex is located on the edge of the Kyzylkum Desert about 70 km from Urgench and consists of three fortresses; a lower, middle and upper fortress. Built to protect the local population from raids by nomads between the 4th century BC and the 7th century AD, the upper fortress is the oldest. The fortresses have been uninhabited for about 1300 years. They were rediscovered and excavated by the archaeologist Tolstov (Russian) around 1940.