Kyrk Kyz Kala, Southern Karakalpakstan

Because the Sultanuizdag ridge protected Lower Khorezm only from the north, the Siyavushids built a chain of frontier defenses along the northeastern and eastern borders in the 4th–3rd centuries BC. The surviving sites include Ayaz Kala I, Minor and Major Kyrk Kyz Kala, Kurgashin Kala, Janbas Kala and Major Guldursun.

Major Kyrk Kyz Kala stands beside the road and measures approximately 250 by 215 metres. Its strongly fortified walls survive up to 12 metres high. The fortress protected one of the principal irrigation channels of the ancient Khorezmian oasis until the 8th century.

A second inner wall created a two-level gallery for archers. Rectangular towers with three-storey internal chambers reinforced the perimeter. Each corner used a paired tower composition known as a dovetail. About ten metres outside the main walls ran an additional protective barrier, or proteichisma.