Hagia Sophia which is situated at the Sultanahmet Square and which is considered as the biggest Christian place of worship for years is one of the most important historical places in İstanbul. According to Theophanes, Nikephoros and Grammarian Leon the first building of Hagia Sophia was erected during the reign of Emperor Constantius I (324-337). The church which was burned down in the year 532 AD took its present form during the reign of Emperor Justinian I. The construction of the church started in 532 and was completed in 537 AD. The interior of the basilica shape construction which is a characteristic example of Byzantine architecture has been decorated with mosaics, coloured marble plates, stained glass and ceiling coverings. Among the mosaics of Hagia Sophia there are important mosaics such as “ Virgin and Child “ in the apse and the mosaics displaying Constantine, Justinian, İmp. Zoe and Eugene on the narthex.
Hagia Sophia was designed by Anthemios of Tralles and Isidoros from Miletos. The central dome is supported by four huge pendentives and among these pendentives there are big piers which seperate the center nave and the side naves and which are connected to each other through wide arches The central dome is supported by half domes in the east and west.
For over 900 years Hagia Sophia has been used as a church where the Orthodox Patriarch was seated. After the conquest of Istanbul in the year 1453 Hagia Sophia was converted into a mosque and the mosaics inside the building were covered to meet the requirements of the Islam Religion. Hagia Sophia which was converted into a museum by Mustafa Kemal in the year 1934 has been taken under protection by UNESCO in the year 1993. The coverage of the basilical infrastructure with a dom in east and west directions has created important problems with time. The restoration works of the building which is being visited as an important center since the past are still in progress. Hagia Sophia may be visited from 09.20 to 16.30 every day except Monday