Hagia Sophia, also called Church of the Holy Wisdom or Church of the Divine Wisdom, cathedral built at Constantinople (now Istanbul, Turkey) in the 6th century ce (532–537) under the direction of the Byzantine emperor Justinian I. By general consensus, it is the most important Byzantine structure and one of the world’s great monuments. The Hagia Sophia was built in the remarkably short time of about six years, being completed in 537 ce. Unusual for the period in which it was built, the names of the building’s architects—Anthemius of Tralles and Isidorus of Miletus—are well known, as is their familiarity with mechanics and mathematics. The Hagia Sophia combines a longitudinal basilica and a centralized building in a wholly original manner, with a huge 32-metre (105-foot) main dome supported on pendentives and two semidomes, one on either side of the longitudinal axis. In plan the building is almost square. There are three aisles separated by columns with galleries above and great marble piers rising up to support the dome. The walls above the galleries and the base of the dome are pierced by windows, which in the glare of daylight obscure the supports and give the impression that the canopy floats on air. The structure now standing is essentially the 6th-century edifice, although an earthquake caused a partial collapse of the dome in 558 (restored 562) and there were two further partial collapses, after which it was rebuilt to a smaller scale and the whole church reinforced from the outside. It was restored again in the mid-14th century. For more than a millennium it was the Cathedral of the Ecumenical Patriarchate of Constantinople. It was looted in 1204 by the Venetians and the Crusaders on the Fourth Crusade.
The Church of the Holy Wisdom, now a museum, it is universally acknowledged as one of the great buildings of the world. Unfortunately nothing remains of the original Hagia Sophia, which was built on this site in the fourth century by Constantine the Great. Constantine was the first Christian emperor and the founder of the city of Constantinople, which he called “the New Rome.” The Hagia Sophia was one of several great churches he built in important cities throughout his empire. Following the destruction of Constantine’s church, a second was built by his son Constantius and the emperor Theodosius the Great. This second church was burned down during the Nika riots of 532, though fragments of it have been excavated and can be seen today. Hagia Sophia was rebuilt in her present form between 532 and 537 under the personal supervision of Emperor Justinian I. It is one of the greatest surviving examples of Byzantine architecture, rich with mosaics and marble pillars and coverings. In 1204 the cathedral was ruthlessly attacked, desecrated and plundered by the Crusaders, who also ousted the Patriarch of Constantinople and replaced him with a Latin bishop. This event cemented the division of the Greek Orthodox and Roman Catholic churches that had begun with the Great Schism of 1054. It also means that most of Hagia Sophia’s riches can be seen today not in Istanbul, but in the treasury of St. Mark’s Basilica in Venice. When the Hagia Sophia was used as a place of worship, both for Christians and then for Muslims, the focus of the building was the east end, directly across from the entrance. This is because Christian churches are traditionally oriented towards the east, and Muslims always pray facing Mecca, which is southeast of Istanbul (the “east” end of the Hagia Sophia actually faces southeast). Thus the bulk of interesting sights are clustered in this area of the Hagia Sophia’s huge interior. The most famous of the Hagia Sophia’s mosaics are on the upper floor, in the galleries. The South Gallery, where the great mosaics are, was used for church councils.When the Hagia Sophia was a mosque, the galleries were the place where women sat during worship services. Today, the galleries provide visitors with a commanding view of the nave from all sides and a closeup view of some of the best Byzantine mosaics to be seen anywhere.