Looking down on the basilica of Saint Sophia, the Blue Mosque is undoubtedly graceful. It owes its name to its founder, Sultan Ahmet I, and its nickname to some 20,000 blue ceramic tiles from Iznik. Built between 1609-1616, it represents one of Istanbul's last major imperial achievements by architect Mehmet Agha. The prayer room, covered in rugs, is lit by 260 windows and crowned by a dome, 43m high.