This is the door of the Kadi Cami from 1499, I was later looking for the Ulu (Great) Mosque, and was told it is the same thing. I am not certain though.

The mosque is one of a series of important buildings along the main street, Ulucanlar Caddesi. You can see the major mosque on that square in the back, the Yılırım Beyazit Camii. Later you will see much more of that one.