By Brian J. Pape, AIA, LEED
Isidore of Miletus and Anthemius of Tralles were the two main Byzantine Greek architects that Emperor Justinian I commissioned to design the cathedral Hagia Sophia in Constantinople from 532 to 537. Hagia Sophia means Holy Wisdom. The church is also known as Ayasofya (Turkish), Sancta Sophia (Latin), and Church of the Divine Wisdom.

construction, Istanbul, 6th century. Photo credit: Dennis Jarvis (CC-BY-2.0) / Encyclopædia Brittanica Inc.
The original church on this site is said to have been built on the foundations of a pagan temple in 325 for Constantine I. The earlier Hagia Sophia, which was burned and destroyed in riots, would have been built mainly out of wood; the new one was of stone, “so that the church should no longer prove combustible.” It became one of the largest, most lavish, and most expensive buildings of all time, according to general consensus.
The architects innovatively combined the longitudinal structure of a Roman basilica and the central plan of a drum-supported dome in order to withstand the high magnitude earthquakes of the region. The Hagia Sophia was repeatedly cracked by earthquakes and then quickly repaired, eventually including the addition of eight Corinthian columns. After a great earthquake in 989 ruined the dome again, officials restored the church by rebuilding the dome with dome ribs and reinforcing the walls from the outside with four buttresses, in which condition the church remains today.
In a wholly original manner, its huge 32-metre (105-foot) main dome is 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 obscure the supports in the glare of daylight and give the impression that the “canopy” floats on air.
After the Turkish conquest of Constantinople in 1453 Mehmed II had the church repurposed as a mosque, and in 1934 Turkish President Kemal Atatürk secularized the Hagia Sophia as a museum. Art historians consider the building’s beautiful mosaics to be the main source of knowledge about the state of mosaic art in the time shortly after the end of the Iconoclastic Controversy in the 8th and 9th centuries. Many basilicas and mosques were modeled on the Hagia Sophia, including the Cathedral Basilica of Saint Louis (St. Louis MO).
The Hagia Sophia is a UNESCO World Heritage site.
FLOOR PLAN of the Hagia Sophia, Istanbul. © RIBA, London and University of London.
HAGIA SOPHIA DOME, showing pendentive construction, Istanbul, 6th century. Image credit: Encyclopædia Britannica, Inc.