The defining image of Istanbul, dominating the skyline with its great dome and six minarets. Completed in 1617 for Sultan Ahmed I, it's still a working mosque, so dress appropriately and avoid prayer times. Enter via the courtyard on the SW side. You step (shoeless) into the blue-tiled prayer hall beneath the main dome and its semi-domes. The mihrab is of finely carved marble, well-lit, and the minbar (pulpit) next to it is visible from almost all parts.