Ayaz Kala, Southern Karakalpakstan

Ayaz Kala consists of three fortresses located about 24 km from Buston village near the saline Ayaz-Kul lake. In antiquity and the early Middle Ages, the complex protected the northern frontier of Lower Khorezm on the right bank of the Amu Darya.

The oldest fortress, Ayaz Kala I, measures approximately 150 by 180 metres and was founded under the Siyavushids in the 4th century BC. It occupies a dominant hilltop about 60 metres above the plain. Outer walls rise to 10 metres, with remains of two-level arched galleries and a labyrinthine gate fortification. In the 3rd century AD the walls were reinforced with semicircular towers.

Ayaz Kala III, covering around five hectares, lies below the hill. Archaeologists found traces of a monumental cruciform building dating from the 4th–2nd centuries BC. Double walls with rectangular towers were added around it in the 1st–2nd centuries AD. A town later grew here, centered on a ruler's palace with more than forty rooms, columned ceremonial halls, a courtyard and a fire temple.

Ayaz Kala II was built in the 7th–8th centuries above the palace, on the hill between the other two fortresses. It probably served as a fortified castle or citadel. A steep ramp led to its gate, while battlements and loopholes protected the upper walls. Declining water supplies eventually caused abandonment, although Ayaz Kala I remained an important Khorezmian border fortress into the 11th–13th centuries.