This is Mevlevi mosque, if you enter there you will notice the monuments to many dervish saints (don't know if that's the proper phrase), since this is a "mevlevihanesi", a dervish meeting-place.
For "Mevlevihane" house of Mevlevis (Dervishes) is an exact translation.By the way I have just seen your pages recently.I am from Afyon,I will add some more commentary soon (I hope:)