Mosque Kok-Gumbaz (1435). In translation means "a blue dome". It was constructed on the bases of earlier building of to Mongolian time with similar planning. Kulyala located on a uniform axis with the mausoleum it became the cathedral mosque of the city. The mosque was once adjoined by summer galleries from which the bases of the square poles supporting arches remained. The inscription on the portal demonstrates that Ulugbek builds the mosque on behalf of the father Shakhrukh. From a majestic sanctuary the central dome construction remained. Diameter of a dome - 46 meters, it is more, than diameter of a dome in Bibi-hanum.

The square hall is topped with the sferokonichesky dome leaning on sixteen a grannik. In corners of massive walls four spiral staircases are built-in. On a part of an external dome the remains of the Koranic texts, which are laid out by a brick mosaic in a mayolikovy frame, are read. In 1438 at the southern wall of the mausoleum, Shamsiddina Kulyala Ulugbek builds makbarat (tomb) for relatives and descendants. Texts on marble gravestones of the 15-17th centuries postponed here from the neighboring cemetery mention names of the Termez seyid. It also gave
late name to the mausoleum Gumbazi-Seyidan (Dome Seyidov).
Makbarat is harmonious and graceful. On walls and a dome fragments of the ornamental painting executed by bright blue paint on purely white field remained.