Two kilometers to the west of Toprak Kala remains of Kyzyl Kala fortress (65x63 m) are located. The lower layers of this fortress belong to the 1st–2nd centuries, i.e. it was founded at the same time as the royal Toprak Kala was built and somehow connected to it historically. From north-western and south-western sides the fortress has square towers and the south-eastern tower served as an entrance and had a ramp along the wall.
The fortress walls are approx. 16m high. Inside the fortress there is a second row of walls parallel to the external walls and separated from them by a 2 meters wide corridor. On the top of exterior wall there are two tiers of arrow loopholes. The walls of some upper premises were decorated with murals and in the ground platform there was a network of underground arched rooms. Kyzyl Kala actively functioned in the 1st–4th centuries but after that it was abandoned.
It was recovered as a frontier garrison fortress only in the 12th – beginning of the 13th century during Khorezmshakhs. Initially Kyzyl Kala could be a guarding post at Toprak Kala as well as castle of a Khorezmian nobleman or grandee.
