These pictures are of the Ulu Camii and were taken in June 2008. The interior was under restoration, but at least some of the - wonderful - caligraphy on the columns and walls were visible.

The large design is a sultan’s ‘tuğra’: a calligraphic monogram, seal or signature of an Ottoman sultan, that was affixed to all official documents and correspondence. It was also carved on his seal and stamped on the coins minted during his reign. Each sultan generally chose the precise form of his ‘tuğra’ on the day of his accession from specimens prepared for him in advance by the court calligrapher. The first ‘tuğra’ belonged to Orhan I (1284–1359), the second ruler of the Ottoman Empire and it evolved until it reached the classical form in the ‘tuğra’ of Sultan Suleiman the Magnificent (1494–1566). From the early 18th century on, the Imperial ‘tuğra’ tended to grow larger and more elaborate, ironically opposite to the size and importance of the Ottoman empire, which was shrinking.

This ‘tuğra’ belongs to Abdülhamid I (1774-1789). The calligraphy is dated 1192 H. (1778-1779).

Correspondent: J.M.Criel, Antwerpen.
Source: (amongst others) Vikipedia.