Hagia Sophia

History

Church of Constantius II

The first church on the site was known as the Magna Ecclesia (Μεγάλη Ἐκκλησία, Megálē Ekklēsíā, 'Great Church') because of its size compared to the sizes of the contemporary churches in the city. According to the Chronicon Paschale, the church was consecrated on 15 February 360, during the reign of the emperor Constantius II (r. 337–361) by the Arian bishop Eudoxius of Antioch. It was built next to the area where the Great Palace was being developed.

According to the 5th-century ecclesiastical historian Socrates of Constantinople, the emperor Constantius had c. 346 "constructed the Great Church alongside that called Irene which because it was too small, the emperor's father [Constantine] had enlarged and beautified". A tradition which is not older than the 7th or 8th century reports that the edifice was built by Constantius' father, Constantine the Great (r. 306–337).

Hesychius of Miletus wrote that Constantine built Hagia Sophia with a wooden roof and removed 427 (mostly pagan) statues from the site. The 12th-century chronicler Joannes Zonaras reconciles the two opinions, writing that Constantius had repaired the edifice consecrated by Eusebius of Nicomedia, after it had collapsed. Since Eusebius was the bishop of Constantinople from 339 to 341, and Constantine died in 337, it seems that the first church was erected by Constantius.

The nearby Hagia Irene ("Holy Peace") church was completed earlier and served as cathedral until the Great Church was completed. Besides Hagia Irene, there is no record of major churches in the city-centre before the late 4th century. Rowland Mainstone argued the 4th-century church was not yet known as Hagia Sophia.

The church is known to have had a timber roof, curtains, columns, and an entrance that faced west. It likely had a narthex and is described as being shaped like a Roman circus. This may mean that it had a U-shaped plan like the basilicas of San Marcellino e Pietro and Sant'Agnese fuori le mura in Rome. However, it may also have been a more conventional three-, four-, or five-aisled basilica, perhaps resembling the original Church of the Holy Sepulchre in Jerusalem or the Church of the Nativity in Bethlehem. The building was likely preceded by an atrium, as in the later churches on the site.

Church of Theodosius II

A second church on the site was ordered by Theodosius II (r. 402–450), who inaugurated it on 10 October 415. The Notitia Urbis Constantinopolitanae, a fifth-century list of monuments, names Hagia Sophia as Magna Ecclesia, 'Great Church', while the former cathedral Hagia Irene is referred to as Ecclesia Antiqua, 'Old Church'. At the time of Socrates of Constantinople around 440, "both churches [were] enclosed by a single wall and served by the same clergy". Thus, the complex would have encompassed a large area including the future site of the Hospital of Samson. If the fire of 404 destroyed only the 4th-century main basilica church, then the 5th century Theodosian basilica could have been built surrounded by a complex constructed primarily during the fourth century.

During the reign of Theodosius II, the emperor's elder sister, the Augusta Pulcheria (r. 414–453) was challenged by the patriarch Nestorius (r. 10 April 428 – 22 June 431). The patriarch denied the Augusta access to the sanctuary of the "Great Church", likely on 15 April 428. According to the anonymous Letter to Cosmas, the virgin empress, a promoter of the cult of the Virgin Mary who habitually partook in the Eucharist at the sanctuary of Nestorius's predecessors, claimed right of entry because of her equivalent position to the Theotokos – the Virgin Mary – "having given birth to God". Pulcheria along with Pope Celestine I and Patriarch Cyril of Alexandria had Nestorius overthrown, condemned at the ecumenical council, and exiled.

The area of the western entrance to the Justinianic Hagia Sophia revealed the western remains of its Theodosian predecessor, as well as some fragments of the Constantinian church. German archaeologist Alfons Maria Schneider began conducting archaeological excavations during the mid-1930s, publishing his final report in 1941. Excavations in the area that had once been the 6th-century atrium of the Justinianic church revealed the monumental western entrance and atrium, along with columns and sculptural fragments from both 4th- and 5th-century churches. Further digging was abandoned for fear of harming the structural integrity of the Justinianic building, but parts of the excavation trenches remain uncovered, laying bare the foundations of the Theodosian building.

The basilica was built by architect Rufinus. The church's main entrance, which may have had gilded doors, faced west, and there was an additional entrance to the east. There was a central pulpit and likely an upper gallery, possibly employed as a matroneum (women's section). The exterior was decorated with elaborate carvings of rich Theodosian-era designs, fragments of which have survived, while the floor just inside the portico was embellished with polychrome mosaics. The surviving carved gable end from the centre of the western façade is decorated with a cross-roundel. Fragments of a frieze of reliefs with 12 lambs representing the 12 apostles also remain; unlike Justinian's 6th-century church, the Theodosian Hagia Sophia had both colourful floor mosaics and external decorative sculpture.

Church of Justinian I (current structure)

On 23 February 532, only a few weeks after the destruction of the second basilica, Emperor Justinian I inaugurated the construction of a third and entirely different basilica, larger and more majestic than its predecessors. Justinian appointed two architects, mathematician Anthemius of Tralles and geometer and engineer Isidore of Miletus, to design the building.

Construction of the church began in 532 during the short tenure of Phocas as praetorian prefect. According to John the Lydian, Phocas was responsible for funding the initial construction of the building with 4,000 Roman pounds of gold, but he was dismissed from office in October 532. John the Lydian wrote that Phocas had acquired the funds by moral means, but Evagrius Scholasticus later wrote that the money had been obtained unjustly.

According to Anthony Kaldellis, both of Hagia Sophia's architects named by Procopius were associated with the school of the pagan philosopher Ammonius of Alexandria. It is possible that both they and John the Lydian considered Hagia Sophia a great temple for the supreme Neoplatonist deity who manifestated through light and the sun. John the Lydian describes the church as the "temenos of the Great God" (Greek: τὸ τοῦ μεγάλου θεοῦ Τέμενος, romanized: tò toû megálou theoû Témenos).

Originally the exterior of the church was covered with marble veneer, as indicated by remaining pieces of marble and surviving attachments for lost panels on the building's western face. The white marble cladding of much of the church, together with gilding of some parts, would have given Hagia Sophia a shimmering appearance quite different from the brick- and plaster-work of the modern period, and would have significantly increased its visibility from the sea. The cathedral's interior surfaces were sheathed with polychrome marbles, green and white with purple porphyry, and gold mosaics. The exterior was clad in stucco that was tinted yellow and red during the 19th-century restorations by the Fossati architects.

The construction is described by Procopius in On Buildings (Greek: Περὶ κτισμάτων, romanized: Peri ktismatōn, Latin: De aedificiis). Columns and other marble elements were imported from throughout the Mediterranean, although the columns were once thought to be spoils from cities such as Rome and Ephesus. According to Cyril Mango, only the porphyry from Egypt was reused for the construction of the church. However, although most of the other marble elements were made specifically for Hagia Sophia, they vary in size.

Mosque (1453–1935)

Constantinople was conquered by the Ottoman forces on 29 May 1453. Sultan Mehmed II entered the city and performed the Friday prayer and khutbah (sermon) in Hagia Sophia. The church's priests and religious personnel continued to perform Christian rites, prayers, and ceremonies until they were compelled to stop. When Mehmed and his entourage entered the church, he ordered that it be converted into a mosque immediately. One of the ʿulamāʾ (Islamic scholars) present climbed onto the church's ambo and recited the shahada ("There is no god but Allah, and Muhammad is his messenger"), thus marking the conversion of the church into a mosque. Mehmed is reported to have taken a sword to a soldier who tried to pry up one of the paving slabs of the Proconnesian marble floor.

As described by Western visitors before 1453, such as the Córdoban nobleman Pero Tafur and the Florentine geographer Cristoforo Buondelmonti, the church was in a dilapidated state, with several of its doors fallen from their hinges. Mehmed II ordered a renovation of the building. Mehmed attended the first Friday prayer in the mosque on 1 June 1453. Aya Sofya became the first imperial mosque of Istanbul. Most of the existing houses in the city and the area of the future Topkapı Palace were endowed to the corresponding waqf. From 1478, 2,360 shops, 1,300 houses, 4 caravanserais, 30 boza shops, and 23 shops of sheep heads and trotters gave their income to the foundation. Through the imperial charters of 1520 and 1547, shops and parts of the Grand Bazaar and other markets were added to the foundation.

Before 1481, a small minaret was erected on the southwest corner of the building, above the stair tower. Mehmed's successor Bayezid II (r. 1481–1512) later built another minaret at the northeast corner. One of the minarets collapsed after the earthquake of 1509, and around the middle of the 16th century they were both replaced by two diagonally opposite minarets built at the east and west corners of the edifice. In 1498, Bernardo Bonsignori was the last Western visitor to Hagia Sophia to report seeing the ancient Justinianic floor; shortly afterwards the floor was covered over with carpet and not seen again until the 19th century.

In the 16th century, Sultan Suleiman the Magnificent (r. 1520–1566) brought two colossal candlesticks from his conquest of the Kingdom of Hungary and placed them on either side of the mihrab. During Suleiman's reign, the mosaics above the narthex and imperial gates depicting Jesus, Mary, and various Byzantine emperors were covered by whitewash and plaster, which were removed in 1930 under the Turkish Republic.

Museum (1935–2020)

In 1935, the first Turkish President and founder of the Republic of Turkey, Mustafa Kemal Atatürk, transformed the building into a museum. During the Second World War, the minarets of the museum housed MG 08 machine guns. The carpet and the layer of mortar underneath were removed and marble floor decorations such as the omphalion appeared for the first time since the Fossatis' restoration, when the white plaster covering many of the mosaics had been removed. Due to neglect, the condition of the structure continued to deteriorate, prompting the World Monuments Fund (WMF) to include the Hagia Sophia in their 1996 and 1998 Watch Lists. The building's copper roof had cracked, causing water to leak down over the fragile frescoes and mosaics. Moisture entered from below as well. Rising ground water increased the level of humidity within the monument, creating an unstable environment for stone and paint. The WMF secured a series of grants from 1997 to 2002 for the restoration of the dome. The first stage of work involved the structural stabilization and repair of the cracked roof, which was undertaken with the participation of the Turkish Ministry of Culture and Tourism. The second phase, the preservation of the dome's interior, afforded the opportunity to employ and train young Turkish conservators in the care of mosaics. By 2006, the WMF project was complete, though many areas of Hagia Sophia continue to require significant stability improvement, restoration, and conservation.

In 2014, Hagia Sophia was the second most visited museum in Turkey, attracting almost 3.3 million visitors annually.

While use of the complex as a place of worship (mosque or church) was strictly prohibited, in 1991 the Turkish government allowed the allocation of a pavilion in the museum complex (Ayasofya Müzesi Hünkar Kasrı) for use as a prayer room, and, since 2013, two of the museum's minarets had been used for voicing the call to prayer (the ezan) regularly.

From the early 2010s, several campaigns and government high officials, notably Turkey's deputy prime minister Bülent Arınç in November 2013, demanded the Hagia Sophia be converted back into a mosque. In 2015, Pope Francis publicly acknowledged the Armenian genocide, which is officially denied in Turkey. In response, the mufti of Ankara, Mefail Hızlı, said he believed the Pope's remarks would accelerate the conversion of Hagia Sophia into a mosque.

On 1 July 2016, Muslim prayers were held again in the Hagia Sophia for the first time in 85 years. That November, a Turkish NGO, the Association for the Protection of Historic Monuments and the Environment, filed a lawsuit for converting the museum into a mosque. The court decided it should stay as a 'monument museum'. In October 2016, Turkey's Directorate of Religious Affairs (Diyanet) appointed, for the first time in 81 years, a designated imam, Önder Soy, to the Hagia Sophia mosque. Since then, the adhan has been regularly called out from the Hagia Sophia's minarets five times a day.

Reversion to mosque (2020–present)

Since 2018, Turkish president Recep Tayyip Erdoğan had talked of reverting the status of the Hagia Sophia back to a mosque, as a populist gesture. On 31 March 2018 Erdoğan recited the first verse of the Quran in the Hagia Sophia, dedicating the prayer to the "souls of all who left us this work as inheritance, especially Istanbul's conqueror," strengthening the political movement to make the Hagia Sophia a mosque once again.

In March 2019, Erdoğan said that he would change the status of Hagia Sophia from a museum to a mosque, adding that it had been a "very big mistake" to turn it into a museum. As a UNESCO World Heritage site, this change would require approval from UNESCO's World Heritage Committee. In late 2019 Erdoğan's office took over the administration and upkeep of the nearby Topkapı Palace Museum, transferring responsibility for the site from the Ministry of Culture and Tourism by presidential decree.

In 2020, Turkey's government celebrated the 567th anniversary of the Conquest of Constantinople with an Islamic prayer in Hagia Sophia. In May, during the anniversary events, passages from the Quran were read in the Hagia Sophia. Greece condemned this action, while Turkey in response accused Greece of making "futile and ineffective statements". In June, the head of Turkey's Directorate of Religious Affairs said that "we would be very happy to open Hagia Sophia for worship" and that if it happened "we will provide our religious services as we do in all our mosques". On 25 June, John Haldon, president of the International Association of Byzantine Studies, wrote an open letter to Erdoğan asking that he "consider the value of keeping the Aya Sofya as a museum".

On 10 July 2020, the decision of the Council of Ministers from 1935 to transform the Hagia Sophia into a museum was annulled by the Council of State, decreeing that Hagia Sophia cannot be used "for any other purpose" than being a mosque and that the Hagia Sophia was property of the Fatih Sultan Mehmet Han Foundation. The council reasoned Ottoman Sultan Mehmet II, who conquered Istanbul, deemed the property to be used by the public as a mosque without any fees and was not within the jurisdiction of the Parliament or a ministry council.

Despite secular and global criticism, Erdoğan signed a decree annulling the Hagia Sophia's museum status, reverting it to a mosque. The call to prayer was broadcast from the minarets shortly after the announcement of the change and rebroadcast by major Turkish news networks. A presidential spokesperson said it would become a working mosque, open to anyone similar to the Parisian churches Sacré-Cœur and Notre-Dame. The spokesperson also said that the change would not affect the status of the Hagia Sophia as a UNESCO World Heritage site, and that "Christian icons" within it would continue to be protected.

Architecture

Hagia Sophia is one of the greatest surviving examples of Byzantine architecture. Its interior is decorated with mosaics, marble pillars, and coverings of great artistic value. Justinian had overseen the completion of the greatest basilica ever built up to that time, and it was to remain the largest church for 500 years until the completion of the abbey church at Cluny in the 12th century.

The Hagia Sophia uses masonry construction. The structure has brick and mortar joints that are 1.5 times the width of the bricks. The mortar joints are composed of a combination of sand and minute ceramic pieces distributed evenly throughout the mortar joints. This combination of sand and potsherds was often used in Roman concrete, a predecessor to modern concrete. A considerable amount of iron was used as well, in the form of cramps and ties.

Justinian's basilica was at once the culminating architectural achievement of late antiquity and the first masterpiece of Byzantine architecture. Its influence, both architecturally and liturgically, was widespread and enduring in the Eastern Christianity, Western Christianity, and Islam alike.

The vast interior has a complex structure. The nave is covered by a central dome which at its maximum is 55.6 m (182 ft 5 in) from floor level and rests on an arcade of 40 arched windows. Repairs to its structure have left the dome somewhat elliptical, with the diameter varying between 31.24 and 30.86 m (102 ft 6 in and 101 ft 3 in).

At the western entrance and eastern liturgical side, there are arched openings extended by half domes of identical diameter to the central dome, carried on smaller semi-domed exedrae, a hierarchy of dome-headed elements built up to create a vast oblong interior crowned by the central dome, with a clear span of 76.2 m (250 ft).The theories of Hero of Alexandria, a Hellenistic mathematician of the 1st century AD, may have been utilized to address the challenges presented by building such an expansive dome over so large a space. Svenshon and Stiffel proposed that the architects used Hero's proposed values for constructing vaults. The square measurements were calculated using the side-and-diagonal number progression, which results in squares defined by the numbers 12 and 17, wherein 12 defines the side of the square and 17 its diagonal, which have been used as standard values as early as in cuneiform Babylonian texts.

Floor

The stone floor of Hagia Sophia dates from the 6th century. After the first collapse of the vault, the broken dome was left in situ on the original Justinianic floor and a new floor was laid above the rubble when the dome was rebuilt in 558. From the installation of this second Justinianic floor, the floor became part of the liturgy, with significant locations and spaces demarcated in various ways using different-coloured stones and marbles.

The floor is predominantly made up of Proconnesian marble, quarried on Proconnesus (Marmara Island) in the Propontis (Sea of Marmara). This was the main white marble used in the monuments of Constantinople. Other parts of the floor, like the Thessalian verd antique "marble", were quarried in Thessaly in Roman Greece. The Thessalian verd antique bands across the nave floor were often likened to rivers.

The floor was praised by numerous authors and repeatedly compared to a sea. The Justinianic poet Paul the Silentiary likened the ambo and the solea connecting it to the sanctuary with an island in a sea, with the sanctuary itself a harbour. The 9th-century Narratio writes of it as "like the sea or the flowing waters of a river". Michael the Deacon in the 12th century also described the floor as a sea in which the ambo and other liturgical furniture stood as islands.

During the 15th-century conquest of Constantinople, the Ottoman caliph Mehmed is said to have ascended to the dome and the galleries in order to admire the floor, which according to Tursun Beg resembled "a sea in a storm" or a "petrified sea". Other Ottoman-era authors also praised the floor; Tâcîzâde Cafer Çelebi compared it to waves of marble. The floor was hidden beneath a carpet on 22 July 2020.

Narthex and portals

The Imperial Gate, or Imperial Door, was the main entrance between the exo- and esonarthex, and it was originally exclusively used by the emperor. A long ramp from the northern part of the outer narthex leads up to the upper gallery.

Upper gallery

The upper gallery, or matroneum, is horseshoe-shaped; it encloses the nave on three sides and is interrupted by the apse. Several mosaics are preserved in the upper gallery, an area traditionally reserved for the Empress and her court. The best-preserved mosaics are located in the southern part of the gallery.

The northern first floor gallery contains runic graffiti believed to have been left by members of the Varangian Guard. Structural damage caused by natural disasters is visible on the Hagia Sophia's exterior surface. To ensure that the Hagia Sophia did not sustain any damage on the interior of the building, studies have been conducted using ground penetrating radar within the gallery of the Hagia Sophia. With the use of ground-penetrating radar (GPR), teams discovered weak zones within the Hagia Sophia's gallery and also concluded that the curvature of the vault dome has been shifted out of proportion, compared to its original angular orientation.

Dome

The dome of Hagia Sophia has spurred particular interest for many art historians, architects, and engineers because of the innovative way the original architects envisioned it. The dome is carried on four spherical triangular pendentives, making the Hagia Sophia one of the first large-scale uses of this element. The pendentives are the corners of the square base of the dome, and they curve upwards into the dome to support it, thus restraining the lateral forces of the dome and allowing its weight to flow downwards. The main dome of the Hagia Sophia was the largest pendentive dome in the world until the completion of St Peter's Basilica, and it has a much lower height than any other dome of such a large diameter.

The great dome at the Hagia Sophia is 32.6 metres (107 ft) in diameter and is only 0.61 metres (2 ft 0 in) thick. The main building materials for the original Hagia Sophia were brick and mortar. Brick aggregate was used to make roofs easier to construct. Due to the material's plasticity, it was chosen over cut stone due to the fact that aggregate can be used over a longer distance. According to Rowland Mainstone, "it is unlikely that the vaulting-shell is anywhere more than one normal brick in thickness".

The weight of the dome remained a problem for most of the building's existence. The original cupola collapsed entirely after the earthquake of 558; in 563 a new dome was built by Isidore the Younger. Unlike the original, this included 40 ribs and was raised 6.1 meters (20 feet), in order to lower the lateral forces on the church walls. A larger section of the second dome collapsed as well, over two episodes, so that as of 2021, only two sections of the present dome, the north and south sides, are from the 562 reconstructions. Of the whole dome's 40 ribs, the surviving north section contains eight ribs, while the south section includes six ribs.

Although this design stabilizes the dome and the surrounding walls and arches, the actual construction of the walls of Hagia Sophia weakened the overall structure. The bricklayers used more mortar than brick, which is more effective if the mortar was allowed to settle, as the building would have been more flexible; however, the builders did not allow the mortar to cure before they began the next layer. When the dome was erected, its weight caused the walls to lean outward because of the wet mortar underneath.

When Isidore the Younger rebuilt the fallen cupola, he had first to build up the interior of the walls to make them vertical again. The architect raised the height of the rebuilt dome by approximately 6 m (20 ft) so that the lateral forces would not be as strong and its weight would be transmitted more effectively down into the walls. He shaped the new cupola like a scalloped shell or the inside of an umbrella, with ribs that extend from the top down to the base. These ribs allow the weight of the dome to flow between the windows, down the pendentives, and ultimately to the foundation.

Buttresses

Numerous buttresses have been added throughout the centuries. The flying buttresses to the west of the building, although thought to have been constructed by the Crusaders upon their visit to Constantinople, were actually built during the Byzantine era. This shows that the Romans had prior knowledge of flying buttresses, which can also be seen in Greece, at the Rotunda of Galerius in Thessaloniki, at the monastery of Hosios Loukas in Boeotia, and in Italy at the octagonal basilica of San Vitale in Ravenna. Other buttresses were constructed during the Ottoman times under the guidance of the architect Sinan. A total of 24 buttresses were added.

Minarets

The minarets were an Ottoman addition and not part of the original church's Byzantine design. Mehmed had built a wooden minaret over one of the half domes soon after Hagia Sophia's conversion from a cathedral to a mosque. This minaret does not exist today. One of the minarets (at southeast) was built from red brick and can be dated back from the reign of Mehmed or his successor Beyazıd II. The other three were built from white limestone and sandstone, of which the slender northeast column was erected by Bayezid II and the two identical, larger minarets to the west were erected by Selim II and designed by the famous Ottoman architect Mimar Sinan. Both are 60 m (200 ft) in height, and their thick and massive patterns complete Hagia Sophia's main structure. Many ornaments and details were added to these minarets on repairs during the 15th, 16th, and 19th centuries, which reflect each period's characteristics and ideals.

Notable elements and decorations

Originally, under Justinian's reign, the interior decorations consisted of abstract designs on marble slabs on the walls and floors as well as mosaics on the curving vaults. Of these mosaics, the two archangels Gabriel and Michael are still visible in the spandrels (corners) of the bema. There were already a few figurative decorations, as attested by the late 6th-century ekphrasis of Paul the Silentiary, the Description of Hagia Sophia. The spandrels of the gallery are faced in inlaid thin slabs (opus sectile), showing patterns and figures of flowers and birds in precisely cut pieces of white marble set against a background of black marble. In later stages, figurative mosaics were added, which were destroyed during the iconoclastic controversy (726–843). Present mosaics are from the post-iconoclastic period.

Apart from the mosaics, many figurative decorations were added during the second half of the 9th century: an image of Christ in the central dome; Eastern Orthodox saints, prophets and Church Fathers in the tympana below; historical figures connected with this church, such as Patriarch Ignatius; and some scenes from the Gospels in the galleries. Basil II let artists paint a giant six-winged seraph on each of the four pendentives. The Ottomans covered their faces with golden stars, but in 2009, one of them was restored to its original state.

Loggia of the Empress

The loggia of the empress is located in the centre of the gallery of the Hagia Sophia, above the Imperial Gate and directly opposite the apse. From this matroneum (women's gallery), the empress and the court-ladies would watch the proceedings down below. A green stone disc of verd antique marks the spot where the throne of the empress stood.

Lustration urns

Two huge marble lustration (ritual purification) urns were brought from Pergamon during the reign of Sultan Murad III. They are from the Hellenistic period and carved from single blocks of marble.

Marble Door

The Marble Door inside the Hagia Sophia is located in the southern upper enclosure or gallery. It was used by the participants in synods, who entered and left the meeting chamber through this door. It is said that each side is symbolic and that one side represents heaven while the other represents hell. Its panels are covered in fruits and fish motifs. The door opens into a space that was used as a venue for solemn meetings and important resolutions of patriarchate officials.

Nice Door

The Nice Door is the oldest architectural element found in the Hagia Sophia dating back to the 2nd century BC. The decorations are of reliefs of geometric shapes as well as plants that are believed to have come from a pagan temple in Tarsus in Cilicia, part of the Cibyrrhaeot Theme in modern-day Mersin Province in south-eastern Turkey. It was incorporated into the building by Emperor Theophilos in 838 where it is placed in the south exit in the inner narthex.

Imperial Gate

The Imperial Gate is the door that was used solely by the Emperor and his personal bodyguard and retinue. At 7 metres (23 ft) it is the largest door in the Hagia Sophia and has been dated to the 6th century. Byzantine sources say it was made with wood from Noah's Ark.

In April 2022, the door was vandalised by unknown assailant(s).

Wishing column

At the northwest of the building, there is a column with a hole in the middle covered by bronze plates. This column goes by different names; the "perspiring" or "sweating column", the "crying column", or the "wishing column". Legend states that it has been moist since the appearance of Gregory Thaumaturgus near the column in 1200. It is believed that touching the moisture cures many illnesses.

Viking inscription

In the southern section of Hagia Sophia, a 9th-century Viking inscription has been discovered, which reads, "Halvdan was here." It is theorized that the inscription was created by a Viking soldier serving as a mercenary in the Eastern Roman Empire.

Mosaics

The first mosaics which adorned the church were completed during the reign of Justin II. Many of the non-figurative mosaics in the church come from this period. Most of the mosaics, however, were created in the 10th and 12th centuries, following the periods of Byzantine Iconoclasm.

During the Sack of Constantinople in 1204, the Latin Crusaders vandalized valuable items in every important Byzantine structure of the city, including the golden mosaics of the Hagia Sophia. Many of these items were shipped to Venice, whose Doge Enrico Dandolo had organized the invasion and sack of Constantinople after an agreement with Prince Alexios Angelos, the son of a deposed Byzantine emperor.

19th-century restoration

Following the building's conversion into a mosque in 1453, many of its mosaics were covered with plaster, due to Islam's ban on representational imagery. This process was not completed at once, and reports exist from the 17th century in which travellers note that they could still see Christian images in the former church. In 1847–1849, the building was restored by Gaspare and Giuseppe Fossati, and Sultan Abdulmejid I allowed them to also document any mosaics they might discover during this process, which were later archived in Swiss libraries.

This work did not include repairing the mosaics, and after recording the details about an image, the Fossatis painted it over again. The Fossatis restored the mosaics of the two hexapteryga (six-winged angels; it is uncertain whether they are seraphim or cherubim) located on the two east pendentives, and covered their faces again before the end of the restoration. The other two mosaics, placed on the west pendentives, are copies in paint created by the Fossatis since they could find no surviving remains of them.

As in this case, the architects reproduced in paint damaged decorative mosaic patterns, sometimes redesigning them in the process. The Fossati records are the primary sources about a number of mosaic images now believed to have been completely or partially destroyed in the 1894 Istanbul earthquake. These include a mosaic over a now-unidentified Door of the Poor, a large image of a jewel-encrusted cross, and many images of angels, saints, patriarchs, and church fathers. Most of the missing images were located in the building's two tympana.

One mosaic they documented is Christ Pantocrator in a circle, which would indicate it to be a ceiling mosaic, possibly even of the main dome, which was later covered and painted over with Islamic calligraphy that expounds God as the light of the universe. The Fossatis' drawings of the Hagia Sophia mosaics are today kept in the Archive of the Canton of Ticino.

20th-century restoration

Many mosaics were uncovered in the 1930s by a team from the Byzantine Institute of America led by Thomas Whittemore. The team chose to let a number of simple cross images remain covered by plaster but uncovered all major mosaics found.

Because of its long history as both a church and a mosque, a particular challenge arises in the restoration process. Christian iconographic mosaics can be uncovered, but often at the expense of important and historic Islamic art. Restorers have attempted to maintain a balance between both Christian and Islamic cultures. In particular, much controversy rests upon whether the Islamic calligraphy on the dome of the cathedral should be removed, to permit the underlying Pantocrator mosaic of Christ as Master of the World to be exhibited (assuming the mosaic still exists).

The Hagia Sophia has been a victim of natural disasters that have caused deterioration to the buildings structure and walls. The deterioration of the Hagia Sophia's walls can be directly attributed to salt crystallization. The crystallization of salt is due to an intrusion of rainwater that causes the Hagia Sophia's deteriorating inner and outer walls. Diverting excess rainwater is the main solution to the deteriorating walls at the Hagia Sophia.

Built between 532 and 537, a subsurface structure under the Hagia Sophia has been under investigation, using LaCoste-Romberg gravimeters to determine the depth of the subsurface structure and to discover other hidden cavities beneath the Hagia Sophia. The hidden cavities have also acted as a support system against earthquakes. With these findings using the LaCoste-Romberg gravimeters, it was also discovered that the Hagia Sophia's foundation is built on a slope of natural rock.

Imperial Gate mosaic

The Imperial Gate mosaic is located in the tympanum above that gate, which was used only by the emperors when entering the church. Based on style analysis, it has been dated to the late 9th or early 10th century. The emperor with a nimbus or halo could possibly represent emperor Leo VI the Wise or his son Constantine VII Porphyrogenitus bowing down before Christ Pantocrator, seated on a jewelled throne, giving his blessing and holding in his left hand an open book.

Southwestern entrance mosaic

The southwestern entrance mosaic, situated in the tympanum of the southwestern entrance, dates from the reign of Basil II. It was rediscovered during the restorations of 1849 by the Fossatis. The Virgin sits on a throne without a back, her feet resting on a pedestal, embellished with precious stones. The Christ Child sits on her lap, giving his blessing and holding a scroll in his left hand. On her left side stands emperor Constantine in ceremonial attire, presenting a model of the city to Mary. On her right side stands emperor Justinian I, offering a model of the Hagia Sophia. The composition of the figure of the Virgin enthroned was probably copied from the mosaic inside the semi-dome of the apse inside the liturgical space.

Apse mosaics

The mosaic in the semi-dome above the apse at the east end shows Mary, mother of Jesus holding the Christ Child and seated on a jewelled thokos backless throne. Since its rediscovery after a period of concealment in the Ottoman era, it "has become one of the foremost monuments of Byzantium". The infant Jesus's garment is depicted with golden tesserae.

Guillaume-Joseph Grelot, who had travelled to Constantinople, in 1672 engraved and in 1680 published in Paris an image of the interior of Hagia Sophia which shows the apse mosaic indistinctly. Together with a picture by Cornelius Loos drawn in 1710, these images are early attestations of the mosaic before it was covered towards the end of the 18th century. The mosaic of the Virgin and Child was rediscovered during the restorations of the Fossati brothers in 1847–1848 and revealed by the restoration of Thomas Whittemore in 1935–1939. It was studied again in 1964 with the aid of scaffolding.

It is not known when this mosaic was installed. According to Cyril Mango, the mosaic is "a curious reflection on how little we know about Byzantine art". The work is generally believed to date from after the end of Byzantine Iconoclasm and usually dated to the patriarchate of Photius I (r. 858–867, 877–886) and the time of the emperors Michael III (r. 842–867) and Basil I (r. 867–886). Most specifically, the mosaic has been connected with a surviving homily known to have been written and delivered by Photius in the cathedral on 29 March 867.

Other scholars have favoured earlier or later dates for the present mosaic or its composition. Nikolaos Oikonomides pointed out that Photius's homily refers to a standing portrait of the Theotokos – a Hodegetria – while the present mosaic shows her seated. Likewise, a biography of the patriarch Isidore I (r. 1347–1350) by his successor Philotheus I (r. 1353–1354, 1364–1376) composed before 1363 describes Isidore seeing a standing image of the Virgin at Epiphany in 1347.

Serious damage was done to the building by earthquakes in the 14th century, and it is possible that a standing image of the Virgin that existed in Photius's time was lost in the earthquake of 1346, in which the eastern end of Hagia Sophia was partly destroyed. This interpretation supposes that the present mosaic of the Virgin and Child enthroned is of the late 14th century, a time in which, beginning with Nilus of Constantinople (r. 1380–1388), the patriarchs of Constantinople began to have official seals depicting the Theotokos enthroned on a thokos.

Emperor Alexander mosaic

The Emperor Alexander mosaic is not easy to find for the first-time visitor, located on the second floor in a dark corner of the ceiling. It depicts the emperor Alexander in full regalia, holding a scroll in his right hand and a globus cruciger in his left. A drawing by the Fossatis showed that the mosaic survived until 1849 and that Thomas Whittemore, founder of the Byzantine Institute of America who was granted permission to preserve the mosaics, assumed that it had been destroyed in the earthquake of 1894. Eight years after his death, the mosaic was discovered in 1958 largely through the researches of Robert Van Nice. Unlike most of the other mosaics in Hagia Sophia, which had been covered over by ordinary plaster, the Alexander mosaic was simply painted over and reflected the surrounding mosaic patterns and thus was well hidden. It was duly cleaned by the Byzantine Institute's successor to Whittemore, Paul A. Underwood.

Empress Zoe mosaic

The Empress Zoe mosaic on the eastern wall of the southern gallery dates from the 11th century. Christ Pantocrator, clad in the dark blue robe (as is the custom in Byzantine art), is seated in the middle against a golden background, giving his blessing with the right hand and holding the Bible in his left hand. On either side of his head are the nomina sacra IC and XC, meaning Iēsous Christos. He is flanked by Constantine IX Monomachus and Empress Zoe, both in ceremonial costumes. He is offering a purse, as a symbol of donation, he made to the church, while she is holding a scroll, symbol of the donations she made. The previous heads have been scraped off and replaced by the three present ones. Perhaps the earlier mosaic showed her first husband Romanus III Argyrus or her second husband Michael IV. Another theory is that this mosaic was made for an earlier emperor and empress, with their heads changed into the present ones.

Comnenus mosaic

The Comnenus mosaic, also located on the eastern wall of the southern gallery, dates from 1122. The Virgin Mary is standing in the middle, depicted, as usual in Byzantine art, in a dark blue gown. She holds the Christ Child on her lap. He gives his blessing with his right hand while holding a scroll in his left hand. On her right side stands emperor John II Comnenus, represented in a garb embellished with precious stones. He holds a purse, symbol of an imperial donation to the church.

His wife, the empress Irene of Hungary stands on the left side of the Virgin, wearing ceremonial garments and holding an eiletarion scroll. Their eldest son Alexius Comnenus is represented on an adjacent pilaster. He is shown as a beardless youth, probably representing his appearance at his coronation aged seventeen.

In this panel, one can already see a difference with the Empress Zoe mosaic that is one century older. There is a more realistic expression in the portraits instead of an idealized representation. The Empress Irene, daughter of Ladislaus I of Hungary, is shown with plaited blond hair, rosy cheeks, and grey eyes, revealing her Hungarian descent. The emperor is depicted in a dignified manner.

Deësis mosaic

The Deësis mosaic (Δέησις, "Entreaty") probably dates from 1261. It was commissioned to mark the end of 57 years of Latin Catholic use and the return to the Eastern Orthodox faith. It is the third panel situated in the imperial enclosure of the upper galleries. It is widely considered the finest in Hagia Sophia, because of the softness of the features, the humane expressions and the tones of the mosaic. The style is close to that of the Italian painters of the late 13th or early 14th century, such as Duccio. In this panel the Virgin Mary and John the Baptist are imploring the intercession of Christ Pantocrator for humanity on Judgment Day. The bottom part of this mosaic is badly deteriorated. This mosaic is considered as the beginning of a renaissance in Byzantine pictorial art.

Northern tympanum mosaics

The northern tympanum mosaics feature various saints. They have been able to survive due to their high and inaccessible location. They depict Patriarchs of Constantinople John Chrysostom and Ignatios of Constantinople standing, clothed in white robes with crosses, and holding richly jewelled Bibles. The figures of each patriarch, revered as saints, are identifiable by labels in Greek. The other mosaics in the other tympana have not survived probably due to the frequent earthquakes, as opposed to any deliberate destruction by the Ottoman conquerors.

Dome mosaic

The dome was decorated with four non-identical figures of the six-winged angels which protect the Throne of God; it is uncertain whether they are seraphim or cherubim. The mosaics survive in the eastern part of the dome, but since the ones on the western side were damaged during the Byzantine period, they have been renewed as frescoes. During the Ottoman period each face was covered with metallic lids in the shape of stars, but these were removed to reveal the faces during renovations in 2009.

Other burials

Selim II (1524 – 15 December 1574)

Murad III 1546–1595

Mustafa I (c. 1600 – 20 January 1639), in the courtyard.

Enrico Dandolo (c. 1107 – June 1205), in the east gallery.

Gli (c. 2004 – 7 November 2020), in the garden.

Works influenced by the Hagia Sophia

Many buildings have been modeled on the Hagia Sophia's core structure of a large central dome resting on pendentives and buttressed by two semi-domes.

Byzantine churches influenced by the Hagia Sophia include the Hagia Sophia in Thessaloniki, and the Hagia Irene. The Hagia Irene was remodeled to have a dome similar to the Hagia Sophia's during the reign of Justinian. Neo-Byzantine churches modeled on the Hagia Sophia include the Kronstadt Naval Cathedral, Holy Trinity Cathedral, Sibiu and Poti Cathedral. Each closely replicates the internal geometry of the Hagia Sophia. The layout of the Kronstadt Naval Cathedral is nearly identical to the Hagia Sophia in size and geometry. Its marble revetment mimics the style of the Hagia Sophia.

The Catedral Metropolitana Ortodoxa in São Paulo and the Église du Saint-Esprit (Paris) both replace the two large tympanums beneath the main dome with two shallow semi-domes. Several churches combine elements of the Hagia Sophia with a Latin cross plan. For instance, the transept of the Cathedral Basilica of Saint Louis (St. Louis) is formed by two semi-domes surrounding the main dome. The church's column capitals and mosaics emulate the style of the Hagia Sophia.

Other examples include the Alexander Nevsky Cathedral, Sofia, St Sophia's Cathedral, London, Saint Clement Catholic Church, Chicago, and the Basilica of the National Shrine of the Immaculate Conception. Several mosques commissioned by the Ottoman dynasty have plans based on the Hagia Sophia, including the Süleymaniye Mosque and the Bayezid II Mosque.

Synagogues based on the Hagia Sophia include the Congregation Emanu-El (San Francisco), Great Synagogue of Florence, and Hurva Synagogue.