The main entrance of the Ulug Beg madrassa is crowned by a hugh arc. But above the actual gate a second arc is constructed with a muqarna construction in it.

The time of building the madrassa 1417-1420 can be situated between the these in Mizdakhan and Bukhara.[br]The 14th century muqarnas of Mizdakhan are of the type you often find in Turkey and Iran: Clear elements are arranged in layers leaning on the end of each other.[br]The 17e century muqarnas in Bukhara are designed as concentric circles around stars.[br]The transition between the layers is realised by connecting the points of the stars.

In between is the muqarna of the Ulug Beg madrassa:[br]The greater part of the rear side is flat. The transition to the half 24-ppointed star in the apex is realised in just a few layers. But below in boths corners is a 6-pointed star. The muqarna doesn't continue in layers of stars but evoluates in rather traditional layers of identifiable elements towards the top. [br]It's clear that you distinguish separate muqarna systems not only by region but also in time. And in Uzbekistan there's no rapture but an evolution from one system to another.