The 33m diameter dome of Hagia Sophia soars 55.6m above the floor of the former church/mosque. To provide rectangle space below, it is flanked by two half-domes. It was reconstructed in 562 AD after an earthquake.

Supporting the massive dome are four triangular pendentives, three of which can be seen here. Two of them have mosaics of seraphim (arch-angels). The one at the bottom of this photo is a painted copy. The mosaics were discovered during a 19th century restoration, when this was still a mosque. In accordance with Islamic rules, their faces were covered. One of them is now uncovered.