Hagia Sophia: The History of a Unique Architectural Masterpiece

Location: Hagia Sophia stands in Istanbul’s historic centre, in the Sultanahmet district. It is located on Sultanahmet Square, directly opposite the Blue Mosque. Topkapı Palace and other major sights in the Old City are also just a few minutes’ walk away.

Significance: Hagia Sophia is one of Istanbul’s most important buildings and one of the finest surviving examples of Byzantine architecture. Its vast dome and expansive interior influenced church architecture for centuries and later also shaped Ottoman mosque design. At the same time, few buildings reflect Istanbul’s Byzantine and Ottoman history as vividly as Hagia Sophia. Since 1985, it has been part of the UNESCO World Heritage Site known as the Historic Areas of Istanbul.

Name: The name Hagia Sophia comes from Greek and means “Holy Wisdom”. It does not refer to a saint named Sophia, but to divine wisdom in the Christian faith. The name was already used for the earlier churches on the site and is documented from at least the 5th century.

First church: The present Hagia Sophia is the third church to have stood on this site. The first was inaugurated in 360 and, known as the “Great Church”, was one of the most important places of worship in Constantinople. It was probably a basilica with a wooden roof. During unrest in 404, it was largely destroyed by fire.

Second church: In 415, a new basilica was inaugurated on the same site. Parts of its monumental entrance survive to this day, including a relief showing twelve sheep, probably representing the apostles. This church also burned down during the Nika Revolt in 532. Emperor Justinian eventually had the uprising violently suppressed. Contemporary accounts speak of tens of thousands of deaths. He defeated his opponents and remained emperor until his death in 565.

The construction of the new Hagia Sophia: Later in 532, Emperor Justinian ordered the construction of a much larger church. He commissioned Anthemius of Tralles and Isidore of Miletus to design it, both of whom had specialised knowledge of mathematics and geometry. Around 10,000 workers are said to have taken part in the construction. On 27 December 537, less than six years after work began, the new Hagia Sophia was inaugurated. Its enormous size and vast interior, crowned by a monumental dome, were especially extraordinary for the time. For many centuries, it ranked among the largest and most important churches in the Christian world.

Emperor Justinian I: Justinian ruled the Eastern Roman Empire from 527 to 565. During his reign, territories in the western Mediterranean were reconquered, Roman law was fundamentally reorganised, and numerous important buildings were constructed. Hagia Sophia became the most important building project of his reign and a visible symbol of his ambition to create a strong Christian empire. According to a later tradition, Justinian is said to have declared at the inauguration that he had surpassed the biblical King Solomon. Whether he actually said these words, however, is uncertain.

Coronation church of the emperors: For centuries, Hagia Sophia was a central setting for Byzantine imperial ceremonies. From the 7th century onwards, most emperors were crowned here by the Patriarch of Constantinople. In this way, religious authority and imperial power were particularly closely linked within Hagia Sophia.

Byzantine Iconoclasm: In the 8th and 9th centuries, the Byzantine Empire was deeply divided over whether Christ, Mary and the saints could be depicted and venerated in images. Opponents of such representations regarded them as a potential form of idolatry and had numerous religious images removed or destroyed. Hagia Sophia was also affected. In 843, the veneration of images was permanently restored. Figurative mosaics were subsequently created again, including the depiction of Mary with the infant Jesus in the apse, dating from around 867.

Earthquakes and the collapse of the dome: Hagia Sophia’s original dome was particularly shallow and structurally very daring. Several earthquakes weakened the building until a large section of the dome collapsed in 558. During reconstruction, the dome was given a higher and steeper shape. This directed more of the forces downwards and less to the sides. The work was supervised by Isidore the Younger, a nephew of the original architect Isidore of Miletus. Hagia Sophia was ceremonially reopened in 562.

The East-West Schism of 1054: In 1054, Hagia Sophia became the setting for a highly symbolic conflict between Rome and Constantinople. During a service, papal envoys placed a document of excommunication on the altar, directed against the Patriarch of Constantinople. A few days later, an assembly of senior church officials in Constantinople responded with its own excommunication of the papal envoys. The incident is regarded as an important milestone in the Great Schism, the growing division between the Western and Eastern Churches. However, the split did not occur on a single day, but developed over centuries from religious, political and cultural tensions.

Looting by the Crusaders: In 1204, participants in the Fourth Crusade captured and looted Constantinople, even though their original destination had been Egypt. Financial problems, Venetian influence and a Byzantine dispute over the throne had diverted the crusade to Constantinople. When promised payments failed to materialise and the situation escalated, the Crusaders attacked the city. Hagia Sophia was also looted. Relics, liturgical objects and other valuables were stolen, and some were taken to Western Europe. Hagia Sophia was then converted into the Catholic cathedral of the newly established Latin Empire. It did not become an Orthodox church again until the Byzantines recaptured Constantinople in 1261.

Conversion into a mosque: After the Ottoman conquest of Constantinople in 1453, Sultan Mehmed II ordered Hagia Sophia to be converted into a mosque. Christian furnishings were removed, altered or incorporated into its new use. Many figurative mosaics were plastered over or covered during the following centuries. At the same time, the Ottomans added features including minarets, a mihrab as a prayer niche and a minbar as a pulpit. The Byzantine core of the building was preserved and continued to be used, altered and expanded over the centuries.

Restorations: Earthquakes and the enormous weight of the dome made repeated repairs and structural reinforcements necessary over the centuries. In the 16th century, the Ottoman architect Mimar Sinan stabilised the building, partly by adding extra buttresses. Between 1847 and 1849, the brothers Gaspare and Giuseppe Fossati restored large parts of Hagia Sophia. During the work, they uncovered and documented Byzantine mosaics, before covering many of them again because the building was still being used as a mosque. From 1931 onwards, the Byzantine Institute under Thomas Whittemore once again began systematically uncovering and studying the mosaics. As a result, numerous major works of Byzantine art became visible again after centuries.

Conversion into a museum: In 1934, the Turkish government under Mustafa Kemal Atatürk decided to convert Hagia Sophia into a museum. It opened to visitors in 1935. Over the following decades, numerous Byzantine mosaics were further uncovered, restored and permanently displayed. This brought the building’s Christian Byzantine past back into clear view alongside its Ottoman features.

Return to use as a mosque: In July 2020, Turkey’s highest administrative court annulled the 1934 decision that had turned Hagia Sophia into a museum. Shortly afterwards, President Recep Tayyip Erdoğan ordered its renewed use as a mosque. On 24 July 2020, Friday prayers were held there for the first time since 1934. UNESCO expressed regret over the decision and criticised the fact that the change in status had taken place without prior consultation. It also voiced concerns about possible consequences for the protection and accessibility of the building. Hagia Sophia nevertheless remained part of the UNESCO World Heritage Site known as the Historic Areas of Istanbul.

Separate areas: Since 15 January 2024, tourist visits and mosque activities have been more clearly separated. Visitors enter through a dedicated entrance leading to the upper gallery. From there, they can see the prayer hall, Byzantine mosaics and other parts of the interior. The new visitor route is intended to reduce disruption to ongoing prayers while still allowing Hagia Sophia to be visited.

Architecture: Hagia Sophia combines the elongated floor plan of a basilica with a large central domed space. This unusual combination shaped later Byzantine church architecture and also influenced Ottoman mosque design. The building consists mainly of brick and mortar and has been repaired and reinforced several times over the centuries. Inside, the builders used valuable varieties of marble, porphyry and, in some cases, reused columns from older structures.

Dome: Hagia Sophia’s main dome rises around 56 metres above the floor and measures approximately 31 metres in diameter. It rests on four massive piers and structures known as pendentives. These curved triangular surfaces transfer the weight of the circular dome onto the square structure below. There are 40 windows around the base of the dome. The incoming light visually softens the base, creating the impression that the dome is floating above the interior.

Imperial Gate and imperial mosaic: The approximately seven-metre-high Imperial Gate was the most important entrance to the main hall and was reserved for the Byzantine emperor and his entourage. Directly above it is a mosaic depicting Christ seated on a throne. An emperor kneels before him, often identified as Leo VI, although his identity has not been conclusively established. Two medallions beside Christ depict Mary and the Archangel Gabriel.

Omphalion: The floor of the main hall also played a role in imperial ceremonies. The Omphalion is a striking area made up of circles of differently coloured marble and played an important part in the ceremonial rituals of the Byzantine court. Its exact function is not known in every detail, but the area was clearly closely connected with imperial ceremonies.

Mosaics: Hagia Sophia preserves numerous important works of Byzantine art. One of the best known is the Deësis mosaic on the southern gallery. It depicts Christ between Mary and John the Baptist, who turn towards him and symbolically ask him to intercede on behalf of humanity. Four six-winged seraphim, angelic beings from Christian tradition, are also depicted at the transitions to the dome. Many figurative mosaics were covered during the Ottoman period and were only uncovered again centuries later.

Light beneath the dome: Before electric lighting was introduced, Hagia Sophia’s interior was illuminated by numerous oil lamps. They hung from above on long chains and spread their light throughout the vast space. Especially in the evening, the many small flames enhanced the solemn atmosphere of the interior. Parts of the suspension systems have survived to the present day.

Calligraphic roundels: Among the most striking Ottoman additions to the interior are eight large roundels bearing Arabic calligraphy. They display the names of Allah, the Prophet Muhammad, the first four caliphs, as well as Hasan and Husayn, two grandsons of Muhammad. The panels, which measure around 7.5 metres across, were created in the 19th century by the calligrapher Mustafa İzzet Efendi and installed during the restoration carried out by the Fossati brothers.

Mihrab and minbar: The mihrab and minbar are among the most important elements of the Islamic interior. The mihrab is the prayer niche and indicates the direction of Mecca. The minbar is an elevated marble pulpit from which the Friday sermon is delivered. Beside the mihrab stand two large bronze candlesticks that Sultan Süleyman had brought to Istanbul after his campaign in Hungary and the capture of Buda in 1526, and placed in Hagia Sophia.

Sultan’s lodge: Near the mihrab is the Sultan’s Lodge, the enclosed prayer area reserved for the Ottoman ruler. The lodge visible today was created during the restoration of 1847 to 1849 and replaced earlier versions. It is elevated and separated from the rest of the prayer hall by an elaborately decorated grille. This allowed the sultan to take part in the service while remaining protected and clearly separated from the rest of the space.

Minarets: Hagia Sophia’s four minarets were added gradually after the Ottoman conquest and date from different construction phases. As a result, they differ slightly in shape, height and proportions. An earlier wooden minaret has not survived. Together with the great dome, the four towers now define Hagia Sophia’s distinctive silhouette.

Ottoman ablution fountain: Hagia Sophia’s Ottoman complex also includes a richly decorated ablution fountain. Sultan Mahmud I had it built in 1740. Such fountains are used for ritual washing before prayer. The şadırvan is supported by eight columns and is one of the most striking Ottoman additions to the complex.

Sweating Column: One of Hagia Sophia’s best-known curiosities is the so-called Sweating Column. Its surface contains a small hole into which visitors traditionally place their thumb before rotating their hand in a full circle. If the spot feels damp, old folk belief says that a wish will come true or an illness will improve. The story is one of the best-known legends associated with the building.

Viking graffiti: Medieval visitors carved runes into the marble on Hagia Sophia’s gallery. One of the best-known inscriptions contains the name Halvdan and is associated with Scandinavian visitors to Constantinople. The graffiti show how international Constantinople already was in the Middle Ages and how far people travelled even then.