The construction of the Muslim temple, started soon after 1236, was completed at the end of the 13th century. The mosque is a preserved architectural construction of the early Golden Horde period. It is the main building of the complex that forms the ensemble of the public centre of Bolgar of the 13th – 14th centuries. Rectangular in its lay-out, its dimensions being 32х34 metres, it had inside 20 columns and was topped by wooden hipped roof. All walls of the mosque were plastered and reinforced by buttresses. On its southern side, it had the mihrab decorated with rich ornamental carving. In its shape and design, the original temple was quite close to the pre-Mongol mosque that was studied on the Bilyar site in 1973 - 1974 and belongs to the type of Oriental hall mosques with the multi-row supports, the portal entrance and one asymmetrically added minaret. In the early 14th century, the mosque underwent the large-scale reconstruction, including the inner redesign: the prayer hall was divided into six naves by six elegant octagonal columns, two doorways and several window openings were cut through, strong towers were added in the corners. Judging by the materials of masonwork and techniques applied, the mosque resembles the constructions of Transcaucasia, the Crimea, Asia Minor, and Mesopotamia. At the same time, it also contains the stylistic elements and motifs of the architecture of the Middle Asia adapted to local climatic conditions. So, from the stylistic point of view, the architecture of the Cathedral Mosque, as well as of the other monuments of the Bolgar site, represents a peculiar northern branch of Oriental architecture. In 2011 – 2012, the Cathedral Mosque underwent a large-scale restoration, including the replacement of the artificial concrete blocks dating back to the restoration carried out in the 60s of the 20th century, restoration of the conservation masonwork, additional arrangement of the original tufaceous blocks, the arrangement of white-stone floors in the inner space of the mosque, the reconstruction of the carved columns and the restoration of the mihrab niche. The eastern corner tower was reconstructed. The eastern and western stone stairs were built.