The Registan contains three madrasahs (schools), the Ulugh Beg Madrasah (1417-1420), Tilya-Kori Madrasah (1646-1660) and the Sher-Dor Madrasah (1619-1636). The Ulugh Beg Madrasah has its imposing portal with lancet arch facing the square. The corners are flanked by the high well-proportioned minarets. The mosaic panel over the entrance arch is decorated by geometrical stylized ornaments. The square-shaped courtyard includes a mosque, lecture rooms and is fringed by the dormitory cells in which students lived. There are deep galleries along the axes. Originally the Ulugh Beg Madrasah was a two-storied building with four domed darskhonas (lecture room) at the corners. The madrasah was one of the best clergy universities in the Moslem Orient of the 15th century. Abdurakhman Djami, a prominent poet, scientist and philosopher studied here. Ulugh Beg himself gave lectures here. During Ulugh Beg's government the madrasah was a centre of secular science.