Quick Answer
Hagia Sophia is not one building but three churches built on the same site in Istanbul, spanning 325 to 1453 CE. The third—Justinian’s famous cathedral completed in 537 CE—is the one that survives, featuring a 55-metre-high dome that rests on four massive piers and has collapsed and been rebuilt multiple times. The building is a chronicle of architecture under pressure: Byzantine cathedral, Ottoman mosque, modern monument. The interior preserves ninth and tenth-century mosaics and is as much a history of engineering crisis as a place of worship.
Three Churches on One Site
The Hagia Sophia that visitors enter today is the third building on this ground. The first church was built between 325 and 360 CE, begun by Constantine and completed by his son Constantius. As the largest imperial church in the city, it was called the Megalo Ekklesia — the Great Church. The name Hagia Sophia, meaning Sacred Wisdom, came into use in the fifth century and stayed. In Turkish, it became Ayasofya.
That earliest church was probably a stone-walled basilica with a timber roof. It opened for worship on 15 October 360 and was burnt down during an insurrection in the fifth century. Theodosius II appointed the architect Rouginos to rebuild it as a basilica, reopening on 8 October 415. That second church lasted just over a century before it, too, was destroyed by fire — this time during the Nika insurrection on 13 January 532. Traces of this building were uncovered in 1935 excavations at a depth of two metres outside the western wall: five marble steps leading to a portico and from there through three portals to a narthex. The church was approximately sixty metres wide.
Justinian’s Building
Thirty-nine days after the fire, Justinian ordered construction of something that had no precedent. He appointed two architects — Anthemios of Tralles and Isidoros of Miletus — and set one thousand master craftsmen and ten thousand labourers to work. After past experience, timber was avoided entirely. Columns were brought from temples at Baalbek, Heliopolis, Ephesus, and Delphi. The marble came from across the empire — white Proconnesian, green Thessalian, golden Libyan, pink Phrygian, ivory Cappadocian. The main walls, dome, vaults, and arches were built of brick.
Construction took five years. The church opened on 27 December 537. Justinian approached in his ceremonial coach, was received by the Patriarch Menas, and they entered arm in arm. According to tradition, the emperor walked toward the apse and declared: “Solomon, I have surpassed you.”
Collapse and Repair
Repeated earthquakes tested the structure. In 558, the dome partially collapsed. The younger Isidoros rebuilt it, raising it by 6.25 metres, and the church reopened in 562. Later repairs failed to provide lasting stability, and the cost of maintenance rose continuously.
The worst damage came not from earthquakes but from people. During the Latin invasion of 1204, crusading soldiers stripped the gilded silver panels flanking the imperial portal, took gold and silver crosses, and seized any available valuables. Crusading monks acquired religious artefacts. It was the greatest damage the cathedral suffered in its history.
When the Paleologue dynasty recaptured the city in 1261, Michael VIII ordered restoration under the monk and architect Ruchas. The buttress walls on the western facade date from this campaign. In 1317, pyramidal buttresses were added to the north and south walls to counter the dome’s outward thrust.
Ottoman Conversion
When Mehmet II took Constantinople in 1453, he found the church in a state of ruin. He led the first Friday prayers there and ordered it converted into a mosque. A mihrab was set into the eastern apse facing Mecca, and a wooden minaret was raised over one of the western cupolas. The mosaics were left untouched at first; under Suleyman I, they were plastered over.
The building acquired its minarets from successive sultans: a brick minaret on the southeast from Mehmet II, a slimmer one on the northeast from Bayezid II, and the two solid western minarets added under Selim II, built by the architect Sinan.
Ottoman Embellishments
The sultans maintained and embellished the structure steadily. A fine marble muezzin gallery was added under Murat III. Two Hellenistic-period marble amphorae were brought from Bergama and placed inside with faucets for ritual washing. Two large candelabra flanking the mihrab came from Buda, captured by Suleyman I during his Hungarian campaign. A white marble mimber and a marble pulpit were added under Murat IV. Mahmut I added a library decorated with Iznik tiles and capable of holding thirty thousand books, along with a fountain, school, and observatory in the mosque court. Four sultans’ mausoleums stand in the eastern garden, alongside the baptistry, which was later converted into a mausoleum.
The Fossati Restoration
The most extensive restoration came under Abdulmecit, between 1839 and 1861, directed by the Italian architect Gaspare Fossati. The dome was stabilised with double iron bands. The roof was re-leaded. Columns that had shifted were restored. The mosaics were uncovered and cleaned — those with cruciform patterns and human figures were replastered, while the imperial gallery received its present appearance. The work took two years.
The large inscription plaques on the walls date from this period, inscribed by the calligrapher Izzet Efendi, who also decorated the dome with verses from the Quran.
Hagia Sophia was declared a national monument and opened as a museum by order of Ataturk on 24 November 1934.
The Interior
The church is entered through the western portal into the exonarthex, then through five portals into the narthex — eleven metres deep and sixty metres long, with polychrome marble revetments on the walls. Nine portals open from the narthex into the main body, the three central ones being the imperial doors.
Over the main portal is a ninth-century mosaic of Christ enthroned. His right hand is raised in blessing; his left holds a book resting on his knee. In roundels to either side stand the Virgin Mary and the angel Gabriel. Prostrated before the throne is the emperor Leo VI.
The total area including narthexes is 7,570 square metres — the fourth largest church in the world. The dome rises 55.60 metres above the floor. It is not quite circular, measuring 30.8 by 31.88 metres, and rests on four main piers joined by four arches. Forty windows pierce the drum. In the pendentives, cherubim painted as tenth-century frescoes look down. In the apse, a ninth-century mosaic shows the Mother of God enthroned with the Christ child.
Along the north wall, three clergy mosaics stand in blind niches: the Patriarchbishop of Antalya, Ignatios, and Saint Ignatios Theophoros, in frontal pose on gold ground. On the south side of the central nave, a section of fine marble mosaic marks the spot where Byzantine emperors were crowned — the omphalos, the symbolic centre of the earth. On the north side, the so-called sweating column, made of porous marble, retains the dampness that pilgrims have been pressing their hands against since Byzantine times.
The Gallery Mosaics
The galleries on three sides hold mosaics of considerable quality. The Deesis in the south gallery — twelfth century, partially destroyed but still exquisite in its small tesserae — shows Christ flanked by the Virgin and John the Baptist on a gold ground. Set into the wall opposite is the tombstone of Enrico Dandolo, Doge of Venice, dated 1205.
Nearby, two imperial mosaics: to the left, an eleventh-century panel of Christ with the Empress Zoe and her third husband Constantine IX. To the right, a twelfth-century panel of the Virgin and child flanked by the emperor Iohannes Comnenos II and the empress Eirene, with their son Alexios on a narrow side panel — his pale, wasted face that of a prince who died in his twenties.
Descending by the imperial ramp and exiting through the southern portal, you pass a Hellenistic bronze door brought from Tarsus. Above it, a mosaic of the Virgin standing with the Christ child: on her right, Constantine offers a model of the city; on her left, Justinian holds a model of Hagia Sophia.
The gilded tesserae throughout were made by laying gold leaf over glass, then sealing it with a further layer of glass paste — a technique that has kept them luminous for over a thousand years.
Frequently Asked Questions
What caused the dome to collapse in 558? A series of earthquakes weakened the structure. The dome’s design—resting on four piers linked by arches with pendentives carrying the weight—was revolutionary but untested at that scale. The original dome was raised and reinforced by Isidoros the Younger, and later repairs added buttressing on the north and south sides. The structure continues to shift and require reinforcement.
Are the mosaics still visible? Some are. Byzantine emperors and saints appear in the galleries on three sides. The most famous is the Deesis in the south gallery, showing Christ flanked by the Virgin and John the Baptist. When Hagia Sophia was converted to a mosque, many were plastered over. The Fossati restoration (1839–1861) uncovered and preserved key examples, though some remain covered to accommodate Muslim worship.
How much of Justinian’s original building survives? The basic structure—the four piers, the main dome and semi-domes, the overall plan—is original. But the building has been substantially rebuilt and reinforced. Later additions include Ottoman minarets, reinforcing buttresses, marble revetments, and religious inscriptions. The interior you see today is a palimpsest of reconstruction campaigns.
What is the sweating column, and is the legend true? A marble column on the north side of the central nave retains dampness that pilgrims have been pressing their hands against since Byzantine times. The moisture is real, but whether it has healing properties is a matter of faith rather than fact. The column is one of the older surviving elements from the Byzantine period.
How many people could Hagia Sophia hold? The interior covers 7,570 square metres, making it the fourth-largest church in the world. The sanctuary was designed to hold the patriarch, the clergy, and the imperial court; the galleries above held the imperial household and other dignitaries. It could accommodate thousands, though exact capacity figures are debated.
Can I visit Hagia Sophia today? It was reconverted to a mosque in 2020 and operates as an active mosque with restricted visiting hours. Non-Muslim visitors can enter during designated times, though access to galleries and certain sections may be limited. Check current guidelines before planning. Modest dress is required, and you must remove shoes.