A series of earthquakes in 553 and 557 caused significant structural damage to the Hagia Sophia, and during such a tremor on 7 May 558, the dome of the basilica collapsed completely, destroying the ambon, altar, and ciborium. The emperor Justinian I ordered an immediate restoration, entrusting the task to the architect Isidorus the Younger, nephew of Isidore of Miletus. Isidorus used lighter materials, supports, and created rows of windows, and elevated the Hagia Sophia’s dome by 10 meters, giving the building its present form. The renovations were completed in 562 and the basilica reopened.
Then the epitome of Byzantine architecture, the Hagia Sopha was later a mosque, and is now a museum in Istanbul, Turkey. From the date of its dedication in 360 until 1453, it served as the Greek Patriarchal cathedral of Constantinople, except between 1204 and 1261, when it was converted to a Roman Catholic cathedral under the Latin Empire. The building was a mosque from 29 May 1453 until 1931, when it was secularized. It was opened as a museum on 1 February 1935. It was the largest cathedral in the world for nearly a thousand years, until Seville Cathedral was completed in 1520.
Reference: Rabun Taylor. “A Literary and Structural Analysis of the First Dome on Justinian’s Hagia Sophia, Constantinople.” Journal of the Society of Architectural Historians. Vol. 55, No. 1 (1996), pp. 66-78.
Hagia Sophia, Istanbul, Turkey: east and west façades. anthemius of Tralles and Isidorus of Miletus, 532-537. Photo: Art Resources, New York City.
Giuseppe Fossati and Gaspare Fossati. Hagia Sophia; one of eight wooden plaques or roundels bearing Arabic calligraphy, 1848. Photo: Art on File.
Hagia Sophia interior. Madonna and Child, flanked by Empress Irene and Emperor John II Komnenos (1118-1134); votive mosaic in the south gallery. Photo: Art Resources, New York City.
Hagia Sophia interior, Anthemius of Tralles and Isidorus of Miletus, 532-537. Photo: Art Resources, New York City.
Further Reading: Robert S. Nelson. Hagia Sophia, 1850-1950: Holy Wisdom Modern Monument. Chicago: University of Chicago Press, 2004.
Judith Herrin. Byzantium: The Surprising Life of a Medieval Empire. Princeton: Princeton University Press, 2007.