The Ulu Camii or Great Mosque in Bursa is a wonderful sight. From the Wikipedia:

"Ulu Cami is the largest mosque in Bursa and a landmark of early Ottoman architecture which used many elements from the Seljuk architecture. Ordered by Sultan Bayezid I, the mosque was designed and built by architect Ali Neccar in 1396–1399. It is a large rectangular building, with twenty domes arranged in four rows of five that are supported by twelve columns. Supposedly the twenty domes were built instead of the twenty separate mosques which Sultan Bayezid I had promised for winning the Battle of Nicopolis in 1396. The mosque has two minarets. There is also a fountain (şadırvan) inside the mosque where worshipers can perform ritual ablutions before prayer; the dome over the şadırvan is capped by a skylight which creates a soft light below, playing an important role in the illumination of the large building.
The horizontally spacious and dimly lit interior is designed to feel peaceful and contemplative. The subdivisions of space formed by multiple domes and pillars create a sense of privacy and even intimacy.
Inside the mosque there are 192 monumental wall inscriptions [...]. The mosque has one of the greatest examples of Islamic calligraphy in the world. The Calligraphy is written on the walls, columns and on small and large plates. The mosque is located in the old city center of Bursa on the Atatürk Blvd."

Concerning the wall inscriptions: All the inscriptions are late-Ottoman and date from the 18th, 19th and even 20th century. The oldest dated calligraphic work goes back to 1770 and is the work of ‘Ali Hoca’, who in his old age became a teacher to the future sultan Mahmut II (1789-1839).

Correspondent: J.M.Criel, Antwerpen.
Sources: ‘Vakıf Abideler ve eski Eserler III’ - Vakıflar Genel Müdürlüğü, Ankara 1983 .
& Many dated works and text plates with explanations (in the Ulu Cami).