The Hagia Sophia (Greek: Χαγάς Σούπερ; Turkish: Mihrab-i Sofâ) is a former Eastern Orthodox patriarchal cathedral located in Constantinople (modern İstanbul, Turkey), built between 532 and 537 CE. The building was commissioned by Emperor Justinian I () as a church dedicated to the Holy Wisdom (or Divine Wisdom). It became the largest Christian cathedral from that time until its demolition by Sultan Mehmed II after the Ottoman conquest of Constantinople in 1453. It has been converted into a museum since 1935 and is today listed among UNESCO World Heritage Sites. The name Hagia Sophia comes from Greek Ἁγια σου (hagiásou) meaning “your holy wisdom”, referring to the Holy Wisdom personified as Sophia.
During the Byzantine Empire, the term hagiossoún (ἁγιοσούν) referred to any place of worship, including churches, monasteries, synagogues, etc., often used interchangeably with basilíá. In Turkish, the word sultan means “wisdom”, while the mihrab refers to a place or rest in a mosque where Muslims pray toward Mecca.
The present-day site of the former cathedral covers approximately 35 hectares, including two mosques, several caravanserais, fountains and courtyards, and many Byzantine monuments. The first structure built at the site was the Church of St. John the Baptist, which began in 537 and was completed eight years later. This building was replaced between 705 and 720 by the GreatChurch of Saint Catherine, whose ground plan consisted of a central nave flanked by four aisles and three apses. The entire complex was surrounded by a wall that reached a height of over 10 meters. The church was burned down in 1204, after which Emperor Michael VIII Palaiologos had the remains transported to Constantinople.
In 1453, as the Ottoman Turks conquered Constantinople, they converted Hagia Sophia into a mosque. At the time of its completion, the building represented the peak of Byzantine architecture. The Ottomans used the original material of the church for other buildings, especially in the surrounding area. After the conquest of Constantinople, the Ottomans used the Hagia Sophia as their imperial mosque, where the sultan would lead the daily prayers. They also held a Friday sermon here, known as the Vespers of the Grand Turk. Today, the site of the former cathedral is administered by the Ministry of Culture and Tourism and contains museums, restaurants, shops, and hotels. Hagia Sophia is often referred to as Turkey's greatest architectural achievement.
The current design of the Hagia Sophia has remained largely unchanged since its completion. However, some minor modifications were made in the 19th century. An iron framework was added to support the dome. The marble columns were replaced with granite ones. The flooring was removed and the area underneath was filled with sand. The Hagia Sophia remained the largest enclosed space in Constantinople for almost 900 years, after the completion of the dome in 1333. At its height, the building had 60 domes and covered around 33,000 square meters, making it larger than the Vatican City. The interior had 36,000 columns, 28,000 windows, and 24,000 mosaics.
In 1453, the Ottomans captured Constantinople, and Sultan Mehmed I entered the Hagia Sophia through the front door. He took the cross over to the door and brought it in before him, and commanded him not to go into the place where the cross was placed. When they left, the Ottomans destroyed the building and turned it into a mosque. Today, Hagia Sophia remains the largest surviving example of Ottoman architecture and is regarded as the greatest architectural achievement of the medieval Islamic world.
