Besides, Byzantine people have learned to build light domes with bricks and ceramic. A mixture of brick, stone and mortar is used as building material. The exterior walls are sober, with a natural finish. The mosaic decorations, mosaics most of the time, are luxurious. T he Basilica of Hagia Sophia in Istambul, is one of the most important Byzantine constructions.
Numerous domes surround the main one as can be appreciated.
The four tall towers at each side of the building were built by the Muslims, who conquered the remainder of the Roman empire.