The Ulugbek Medressa, on the western side of the Registan, is the square's original medressa, finished in 1420 under Ulugbek who is said to have taught mathematics here (the stars on the portal reflect Ulugbek's love of astronomy). Beneath the little corner domes were lecture halls, now housing displays on Ulugbek, and at the rear there is a large mosque with a beautiful blue painted interior and an austere teaching room to one side.

　　Police guards occasionally offer to clandestinely escort visitors to the top of the medressa's minaret for around US$10.