Ayaz Kala is a fortress dating back to end of the 4th or beginning of the 3rd century BCE. In this time Khorezm had become independent from Persia. Ayaz Kala 1 was part of a chain of fortresses protecting the agricultural settlements from attacks by nomads. The fortress is situated on the top of a hill, approximately 100 m (330 ft) high, providing wide views over the surrounding plains. The fortress is rectangular in plan with sides 182 and 152 m (597 and 499 ft) long. The main axis is oriented from south to north.[4][5] At the southern end of the axis is a square gateway, which is a typical element of frontier fortresses of Khorezm. The enemies' approach lies parallel to the south east walls and invaders were vulnerable to attack from above. A massive gateway defended by two rectangular towers leads into a small rectangular chamber. This chamber was overlooked on all sides by high walls from which bowmen could shoot at the enemy in case the first gate was breached.

The Kyzyl-Kala fortress is located in the territory of Ancient Khorezm (modern Karakalpakstan) in the vicinity of ancient town Toprak-Kala. Kyzyl-Kala is a monument of the last stage of antique Khorezm architectural history and can be considered as a prototype of the Afrigid period castles corrugated with massive columns.This architectural site was discovered during a Khorasan expedition headed by S.P. Tolstov in 1938. All basic study of the fortress was conducted by the expedition staff. The fortress itself is not large in size and almost square in form. The study of the foundation and the structure ruins showed that the fortress was surrounded with a double vallum, and there were watchtowers in every corner of the fortress. A main street in the center of the settlement led to a temple of fire-worshippers where Zoroastrian priests were holding their sacramental rites. The residential part of the city was divided by a street into several sections with several rooms in each