One of some pictures I took of an ablutions fountain that stands close to the entrance to the area.
From an offical site on the web I gathered: "Hagia Sophia Fountain built by Sultan Mahmud I (1730 - 1754) in 1740 is a masterpiece of Ottoman Architecture and one of the largest and most beautiful fountains in Istanbul. It is covered by a dome and an eave mounted on eight columns with muqarnas headings and eight arches. On the dome, there are a bronze tulip scripture of "Allah" written by carving in stack on top and a mirror scripture of "Muhammed" below and an "eulogium" on the upper and inner part of marble arcade. The fountain has 16 slices and each slice have bronze taps in the middle. There are tulip-shape bronze banners containing the scripture of "We have created everything from water" on the upper part of the joining section of sliced bronze water mains over the taps."