“Ulu Cami” (The Grand Mosque) was built by Yıldırım Bayezid between 1396 and 1399. After the victory at Nicopolis (Niğbolu) in 1396, Yıldırım Bayezid wanted to built 20 masjids in Bursa, but on suggestion of Emir Sultan, his son-in-law and one of the period’s important scolar men, he built only one, the “Ulu Cami”, or Grand Musjid, covering it with 20 domes, the Ulu Cami is truly an architectural marvel adorned inside with nearly 200 calligraphic inscriptions. Every corner of this building has unique historical details. 

The domes with a diameter of 11 m each sit on arches and pendatives, which interconnect the twelve massive, square-plan pillars to the thick main walls. The dome at this Musjid’s central section is covered with a glazing. Beneath it, there is a big ablution fountain with 16 corners.

The prayer hall is divided into 20 bays of equal size by 12 cruciform piers and arches adjoining the walls; each bay is covered by a dome. One of the domes situated in the bays along the axis formed by the north portal and the mihrab is open to the sky; beneath it is a fountain. Despite the fact that there are two rows of windows and that the drums of the domes have openings to let in light, very little natural daylight enters the prayer hall.