The Ulu Camii or Great Mosque of Bursa is a venerable and quite pleasant building, dating from 1396. The Lonely Planet guide compares it to the Erzerum Ulu Camii, but I disagree, that one is much darker and though nice does not give me the delight I always feel in the Bursa one.
This series I took during a December 2006 visit. Some shots on the outside, some on the inside (where a restoration was going on). This is some of the trade going on outside.