Hagia Sophia

Hagia Sophia (Greek Ἁγία Σοφία, “Holy Wisdom”; Turkish Ayasofya) stands on the tip of the historic peninsula of Istanbul, between the Golden Horn and the Sea of Marmara. For more than nine hundred years it was the cathedral of Constantinople, the capital of the Eastern Roman (Byzantine) Empire, and the church of the Patriarch of Constantinople, the senior bishop of the Eastern Orthodox world. The name does not refer to a saint called Sophia: the church was dedicated to Christ as the Wisdom of God.

The building we see today is the third church on the site. It was built for Emperor Justinian I between 532 and 537 after the previous church had been burned during a violent uprising. It was the largest enclosed interior space in the world for centuries, and its central dome, resting on four curved triangles of masonry called pendentives, was a daring piece of engineering.

Hagia Sophia has had four lives. It was a Christian cathedral from 537 to 1453 (with a Latin Catholic interval after the Fourth Crusade), an Ottoman imperial mosque from 1453 to the 1930s, a museum of the Turkish Republic from 1935 to 2020, and, since July 2020, a functioning mosque once more. Each period has left its mark on the building, so that Byzantine mosaics and Ottoman calligraphy now share the same walls.

From outside, Hagia Sophia looks like a mountain of domes and buttresses, with four slender Ottoman minarets at its corners. Much of this bulk was added over the centuries to hold the building up. The original idea is easier to see from inside.

Visitors enter from the west through two long entrance halls, the outer and inner narthex. The central door, the Imperial Gate, was once reserved for the emperor. Beyond it opens the nave, the great central space. Its core is a square about 31 m on each side, marked by four massive piers. Arches spring from pier to pier, and between the arches four pendentives curve upward and inward to form a circle on which the dome sits. To the east and west, two half-domes extend the space, and smaller semi-domes (exedrae) spread out from them, so that the eye travels upward in a cascade of curves toward the main dome.

Around the base of the dome runs a ring of forty windows. Light entering through them, and through many other windows in the walls, dissolves the heavy structure so that the dome appears to hover. The historian Procopius, who saw the new church, wrote that the dome seemed not to rest on solid masonry but to hang from heaven on a golden chain.

On three sides the nave is surrounded by aisles and, above them, broad galleries shaped like a horseshoe. In Byzantine times the galleries were used by the empress and her court, among others; a green stone disc on the western gallery marks where the empress’s seat is thought to have been. At the far east end is the apse, the curved sanctuary where the altar stood. In the Ottoman period a mihrab (a niche showing the direction of Mecca) was placed there, set slightly off the church’s axis because Mecca lies to the south-east.

The first “Great Church” on the site was dedicated in 360 under Emperor Constantius II. It was burned in 404 during riots connected with the exile of the bishop John Chrysostom. A second church, built under Theodosius II, was dedicated in 415. Remains of its colonnaded entrance can still be seen in front of the present building.

In January 532, supporters of Constantinople’s two chariot-racing factions, the Blues and the Greens, united against Justinian in the Nika riots, named after their cry “Nika!” (“Conquer!”). Much of the city centre was burned, including the second Hagia Sophia. The revolt was crushed with great bloodshed in the Hippodrome; ancient sources speak of tens of thousands killed.

Only weeks later Justinian began rebuilding on a scale no one had attempted. The new cathedral would show that the emperor had restored order and that his rule was blessed by God. It was dedicated on 27 December 537, less than six years after the riots. A later legend says that on entering the finished church Justinian exclaimed, “Solomon, I have surpassed you!”, comparing it with the Temple in Jerusalem, but this story comes from a much later text and is not regarded as historical.

Justinian entrusted the project to two men described in the sources as mechanikoi, experts in geometry and mechanics rather than builders in the modern sense: Anthemius of Tralles, a mathematician who wrote on optics and burning mirrors, and Isidore of Miletus, a geometer who edited works of Archimedes. Their design combined the long axis of a basilica, the traditional church plan, with the centralized form of a domed building.

The walls and vaults were built mainly of brick laid in very thick beds of mortar, with stone for the piers. Marble came from across the Mediterranean: white marble from the island of Proconnesus in the Sea of Marmara, green stone from Thessaly, and red-purple porphyry from Egypt. Older legends claimed that the columns were plundered from pagan temples; modern scholars think most marble was quarried new, although the porphyry may have been reused. Iron cramps and ties helped hold the masonry together.

Speed had a cost. The mortar was not given time to harden before the next courses were laid, and the weight of the shallow first dome pushed the piers and walls outward. After earthquakes in 553 and 557, part of the dome collapsed in 558. Isidore the Younger, the nephew of Isidore of Miletus, rebuilt it about 6 m higher, with a steeper profile and forty ribs, which reduced the outward thrust. The church was rededicated on 24 December 562; the poet Paul the Silentiary composed a long verse description for the occasion.

Later earthquakes brought partial collapses in 989 and 1346. After the first, the Armenian architect Trdat rebuilt the western arch and part of the dome; after the second, repairs were carried out in the 1350s. Because of these repairs the dome is today slightly elliptical, and only parts of the sixth-century shell survive. Buttresses were added by Byzantine emperors and, in the sixteenth century, by the Ottoman architect Mimar Sinan, whose reinforcements are credited with helping the building survive later earthquakes.

For Byzantines, Hagia Sophia was simply the Great Church (Megale Ekklesia). It was the setting for the solemn liturgy of the capital, for coronations of emperors and for major church councils and ceremonies. Emperor and patriarch met here in a ritual that displayed the ideal harmony of church and state. In 1054 papal legates laid a bull of excommunication against Patriarch Michael Cerularius on the altar of Hagia Sophia, an event traditionally taken as the symbolic start of the schism between the Catholic and Orthodox churches.

The Russian Primary Chronicle tells how envoys of Prince Vladimir of Kyiv attended a service here in the 980s and reported that they did not know whether they were in heaven or on earth; according to the chronicle, this helped persuade Vladimir to adopt Christianity from Constantinople. Whether or not the story is literally true, it expresses how the building was meant to make worshippers feel.

Justinian’s church was decorated mainly with marble panelling, gold mosaics and crosses rather than human figures. During the period of Iconoclasm (726–787 and 814–842), when religious images were banned, figurative art was rejected. After images were restored in 843, figural mosaics were added over the following centuries. The most famous include the Virgin and Child in the apse, inaugurated with a sermon by Patriarch Photius in 867 (though the date of the surviving image is debated); the panel over the southwest entrance showing the emperors Constantine and Justinian offering the city and the church to the Virgin; portraits of emperors and empresses in the south gallery; and the Deësis, a moving image of Christ between the Virgin and John the Baptist, probably made soon after 1261.

In 1204 the armies of the Fourth Crusade, which had turned against Constantinople, sacked the city. Hagia Sophia was looted; many treasures and relics were carried to Venice and other Western cities. For the next fifty-seven years it served as a Latin Catholic cathedral under the crusader rulers. Enrico Dandolo, the Doge of Venice who led the attack, was buried in the church; a marker placed in the nineteenth century still shows the probable spot in the east gallery.

The Byzantines recovered their capital in 1261, but the restored empire was poor and shrinking. Earthquake damage in the fourteenth century was repaired with difficulty. By the early fifteenth century visitors described the church as dilapidated.

On 29 May 1453 the Ottoman sultan Mehmed II captured Constantinople. The city was sacked for three days, and people who had taken refuge in Hagia Sophia were captured or killed. Mehmed then ordered the church converted into a mosque, and Friday prayers were held there soon after. For Orthodox Christians the fall of the city and the loss of their great church became a lasting symbol of catastrophe; for Ottomans and later Turks, the conquest was a founding triumph, remembered as the fulfilment of a hadith said to praise the conqueror of Constantinople.

As a mosque, Ayasofya was the first imperial mosque of Istanbul and was richly endowed by a charitable foundation (waqf). The Ottomans added a mihrab and minbar (pulpit), and over time four minarets, the first built soon after the conquest and the two large western ones by Sinan in the later sixteenth century. Mosaics showing human figures were gradually covered with plaster or paint, though travellers’ reports show that some remained visible for a long time. Around the building grew tombs of sultans, a school, a fountain for ablutions and other structures.

Hagia Sophia deeply influenced Ottoman architecture. Sinan studied its structure while strengthening it and sought to equal and surpass its dome in his own mosques, such as the Süleymaniye in Istanbul and the Selimiye in Edirne. The Sultan Ahmed Mosque (the “Blue Mosque”), completed in the early seventeenth century directly opposite, also develops the central-dome-and-half-domes scheme.

Between 1847 and 1849 Sultan Abdülmecid I commissioned the Swiss-Italian architects Gaspare and Giuseppe Fossati to restore the building. They consolidated the dome with an iron chain, straightened columns, and recorded mosaics they uncovered before covering them again. Eight huge round wooden panels painted by the calligrapher Kazasker Mustafa İzzet Efendi with the names of God, the Prophet Muhammad, the first four caliphs and the Prophet’s grandsons Hasan and Husayn were hung in the nave, where they remain today.

After the founding of the Republic of Turkey, the building was closed in 1931 for restoration. From that year the Byzantine Institute of America, led by Thomas Whittemore, began uncovering and conserving the mosaics. A decision of the council of ministers in 1934 turned Hagia Sophia into a museum, which opened in 1935. For the secular republic under Mustafa Kemal Atatürk, the museum presented the building as a shared heritage of humanity rather than the property of one faith. It became the most visited monument in Turkey, and in 1985 it was included in the UNESCO World Heritage Site of the Historic Areas of Istanbul.

Calls to reopen it as a mosque grew stronger in later decades. On 10 July 2020 Turkey’s highest administrative court, the Council of State, annulled the 1934 decision, ruling that the building belonged to the foundation established by Mehmed II and could not be used for any purpose other than as a mosque. President Recep Tayyip Erdoğan then transferred it to the Directorate of Religious Affairs, and Friday prayers were held on 24 July 2020.

The change was celebrated by many Muslims in Turkey and elsewhere as the restoration of a mosque. It was criticized by the Greek government, by leaders of Orthodox and other churches, by UNESCO and by some Turkish writers and politicians, who argued that a universal monument was being used for national and political purposes. Today the building is officially the Hagia Sophia Grand Mosque. It remains open to visitors outside prayer times; during prayers the Christian images facing the prayer area, such as the apse mosaic, are covered with curtains or concealed by lighting. Questions about access, conservation and the protection of the Byzantine decoration remain the subject of international discussion.

Hagia Sophia set a standard for sacred architecture in three traditions. In the Orthodox world, cathedrals named after Holy Wisdom rose in Kyiv, Novgorod and elsewhere, and the domed church became the typical form of Byzantine and Slavic church building, though usually on a far smaller scale. In the Islamic world, it shaped the classical Ottoman mosque from the fifteenth to the seventeenth centuries. In the West, nineteenth- and twentieth-century architects built neo-Byzantine churches that consciously echoed its dome and half-domes.

The Pantheon in Rome has a wider dome, but that dome sits on a solid circular drum. Hagia Sophia’s achievement was to raise a dome of more than 30 m high above a square space opened up on all sides, and for many centuries it enclosed the largest interior in the world. It has been studied by engineers as a laboratory of how large masonry structures respond to earthquakes.

Finally, Hagia Sophia is a symbol whose meaning changes with the viewer: for Orthodox Christians the lost heart of Byzantium; for many Turks a monument of the 1453 conquest; for secular Turks and many international visitors, a museum that stood for coexistence. Understanding the building means understanding all of these stories together.

The first dome. Justinian’s original dome of 537 no longer exists, and its shape must be reconstructed from Procopius, from the chronicle of John Malalas and Theophanes on the collapse of 558, and from analysis of the surviving piers, arches and pendentives. Most reconstructions assume a shallower dome, perhaps continuous with the pendentives, but the exact profile, the role of the windows, and the relative importance of hasty construction, earthquake damage and pier deformation in the collapse are still discussed by structural engineers and historians such as Rowland Mainstone and the contributors to Mark and Çakmak’s collected volume.

Design and measurement. The design has been analysed as an exercise in geometry by architects trained in mathematics. The side of the central square, roughly 31 m, was long thought to equal 100 Byzantine feet; the architectural historian Helge Svenshon has proposed instead a value of 99 feet, related to the ancient side-and-diagonal number series (70 : 99) that approximates √2. Such proposals are attractive but difficult to prove in a structure that has deformed and been repaired many times.

Dating the mosaics. The date of the apse Virgin and Child is disputed. Some scholars identify it with the image Photius described in 867; others note that Photius spoke of a standing Virgin whereas the mosaic shows her seated, and date the present image before Iconoclasm, after the earthquake of 989, or even to the late fourteenth century after the collapse of 1346. The Deësis panel is usually dated to after 1261 on stylistic grounds, but this, too, rests on comparison rather than inscription.

Heritage and meaning. Since 2020, scholars have debated how World Heritage principles apply to a living religious building with a contested history: whether “outstanding universal value” requires museum status, how the rights of a state and religious community should be balanced against international interest, and how the display of Christian art in a mosque should be managed. These are questions of law, ethics and politics as much as of art history.

Written sources. The most important contemporary text is Procopius of Caesarea’s On Buildings (De aedificiis), written in praise of Justinian; its first book opens with Hagia Sophia. It is an eyewitness description but also a panegyric, so its claims about divine inspiration and the emperor’s personal role must be read critically. Paul the Silentiary’s verse ekphrasis for the rededication of 562 describes the furnishings, lighting and liturgical arrangements in detail. Chroniclers such as John Malalas and Theophanes record the collapses. The ninth-century Narratio on the construction of Hagia Sophia is full of legends, including the Solomon saying, and is valued more for later Byzantine attitudes than for facts about the sixth century.

Visual and archival sources. Drawings by Western travellers, the documentation of the Fossati restoration (now kept in the Canton of Ticino in Switzerland), and the photographs and reports of the Byzantine Institute in the 1930s are essential for knowing which mosaics existed and how much has been restored or lost, for example in the Istanbul earthquake of 1894.

The building itself. Brick stamps, mortar analysis, building joints and deformations reveal phases of construction and repair. In recent decades engineers have used surveys, laser scanning, ground-penetrating radar, gravimetry and computer models of seismic behaviour to study the structure, and excavations around the building have uncovered remains of the fifth-century church and its surroundings. A large conservation programme to strengthen the dome against earthquakes was under way in the mid-2020s.

Methodological lesson. Hagia Sophia is not a single sixth-century monument but a palimpsest of Byzantine, Latin, Ottoman and Republican interventions. Researchers must separate these layers, while recognizing that each layer is also part of the building’s history.