This is the Hürrem Çavuş Camii, by Sinan. The Strolling through Istanbul guidebook tells us restorations in 1844 and 1901 are perhaps the reason it has lost all its charm it may once have had “except for the garden in which the pleasant imam takes great delight”. Well, the garden seems to be paved over, and the caretaker (I doubt if he had imam status) had no charm at all when he ordered me out.

A çavuş is a messenger.