Cathedral Mosque of Kayalyk – the largest in size structure, archaeologically investigated on the site. Its external dimensions are 38x32 m. Exterior walls are made of mud brick.
Basis and partially bases of columns of rounded river cobbles and bricks were found in a special order at the opening of the mosque. On these columns the wooden roof support was situated; 54 bases in total that divide the interior space into nine aisles. Mosque's walls were plastered; they were arranged by kana (channels) – Medieval heating system, routed so that it took the air, warmed in the oven. Wall thickness of 1.7-2 m were preserved to a height of 2 m. Mihrab built of burnt bricks was arranged opposite the entrance on southwest wall.
Cathedral Mosque of Kayalyk has direct analogues in other capital cities of the Golden Horde, Ak Orda, Mogolistan. Construction of the mosque dates from the second quarter of the XIII century, which is confirmed by the coins found on the floor. The mosque burned during a citywide fire.