Hello Safet and All - I have linked several photos here for the group (not sure if there is another way to post them). They are taken inside the Ulu Camii in Bursa which was the main mosque for the Ottoman Sultans when the capital was in Bursa. I add these because there is an unusual motif of single letters in the mosque, the most common one being 'waw' most likely standing for the kuranic divine name 'al Wadud' (the Loving One). There are other letters such as Jim, but the preponderance of the letter waw might ahve to do with what you see in the final photo, another excpetion in mosque architecture: the turban of the Mevelvi dervish order is included in the calligraphy, something very unusual.