ior also features a "small, sparsely-decorated mihrab," the traditional niche found in mosques which indicates the direction of Mecca, toward which Muslims direct their prayers.
On the exterior each side of the octagon is divided into seven tall panels, of which five have windows. These windows were filled with stained glass in the Ottoman era but probably were first designed to hold marble tracery, with protective iron tracery on the outside. There are four entrances, facing the cardinal points of the compass, and each features a porch. The exterior of the building was originally covered in marble and mosaics, much like those that remain on the interior surfaces, but they were all replaced with Ottoman tiles. The regilded copper roof can be seen from a great distance and is one of the most prominent monuments in the city.
The style of the building derives directly from Byzantine architecture. Domed octagonal churches of this type were fairly common throughout the Byzantine empire and examples existed in the Middle East, such as the Shrine
...