Hagia Sophia

Somewhere in the upper gallery, on a marble parapet overlooking the nave, a Viking scratched his name. The letters are runic and worn nearly smooth, but scholars can still make out part of "Halfdan." He was probably a member of the Varangian Guard, the Scandinavian mercenaries who served the Byzantine emperors, and he was probably bored. The liturgy below him would have gone on for hours in a language he did not speak. So he did what bored men have done in every century: he carved graffiti into the most important building in the known world.

That parapet is still there. You can lean over it and look down into the same space he looked down into, roughly eleven hundred years later.

Two Mathematicians And A Dare

The building Halfdan stood in was not the first church on the site. Two earlier ones had burned, the second during the Nika riots of 532, when a mob nearly threw Emperor Justinian off his throne. Once the revolt had been put down, Justinian ordered a replacement. He did not hire the usual architects. He hired Anthemius of Tralles, a physicist and geometer, and Isidore of Miletus, who taught mathematics. He wanted something nobody had built before: a vast round dome floating over a rectangular hall.

The trick that made it possible was the pendentive, a curved triangular section of masonry that carries the weight of a circle down onto four square corners. Pendentives existed before, but never on anything like this scale. The church was finished in under six years and dedicated at the end of 537. A later chronicler has Justinian walking in and declaring that he had outdone Solomon. The source is centuries removed from the event, so the quote is a story, not a record. The building is the record.

The Dome That Fell

The original dome lasted about twenty years. Earthquakes in the 550s cracked the structure, and in 558 a large section of the dome collapsed into the nave, destroying the altar and pulpit beneath it. Justinian was still alive to see it. The repair went to Isidore the Younger, nephew of one of the original architects, who rebuilt the dome steeper and taller so that it pushed outward less. What you see overhead today is that second design, patched again after further partial collapses in 989 and 1346. Every few centuries the building has needed someone to catch it.

Whose Building It Was

For nearly nine hundred years it was the coronation church of the Eastern Roman Empire. In 1054, papal legates from Rome walked in and laid a bull of excommunication on the altar, the moment usually taken as the formal split between the Latin and Greek churches. In 1204 the Fourth Crusade, meant for Jerusalem, sacked Constantinople instead; the church was looted and served as a Catholic cathedral under the Latin Empire until the Byzantines retook the city in 1261.

In 1453 Mehmed II entered Constantinople and converted the church into a mosque. The four minarets went up under different sultans over the following century and a half. In the 1500s the architect Sinan added the heavy buttresses that help hold the spreading dome in place to this day. The mosaics were not destroyed; they were plastered over, which is why an American team from the Byzantine Institute could uncover them again in the 1930s, revealing faces of Christ, the Virgin, and assorted emperors that nobody had seen for centuries.

In 1934 the Turkish Republic's cabinet turned the building into a museum. In July 2020 the Council of State annulled that decision, and it reopened for Muslim worship as a mosque.

A Detail Worth Passing On

The great bronze doors on the south side of the narthex are older than the building. They were made in the second century BC for a pagan temple, probably in Tarsus, and brought to Constantinople in 838 to be installed here. So the building that has changed religion three times has, at its entrance, a doorway that had already changed religion once before it arrived.

Now

Hagia Sophia is administered as a mosque by Turkey's Directorate of Religious Affairs and has been part of the Historic Areas of Istanbul World Heritage Site since 1985. A major restoration of the dome began in the 2020s, with scaffolding inside and engineers assessing the lead sheathing and the centuries of stress in the masonry.

The permanent threat is the North Anatolian Fault, which runs beneath the Sea of Marmara just south of the city. The building has survived earthquakes since the sixth century, and it has failed in several of them. Each time, someone rebuilt it. The names on the deed have kept changing; the dome, more or less, has stayed.