This soaring edifice is perhaps the greatest work of Byzantine architecture and for almost a thousand years, starting from its completion in 537, it was the world's largest and most important religious monument. As Emperor Justinian may well have intended, the impression that will stay with you longest, years after a visit, is the sight of the dome. As you enter, the half domes trick you before the great space opens up with the immense dome, almost 18 stories high and more than 30 meters (100 feet) across, towering above—look up into it and you'll see the spectacle of thousands of gold tiles glittering in the light of 40 windows. Only Saint Peter's in Rome, not completed until the 17th century, surpasses Hagia Sophia in size and grandeur. It was the cathedral of Constantinople, the heart of the city's spiritual life, and the scene of imperial coronations. It was also the third church on this site: the second, the foundations of which you can see at the entrance, was burned down in the antigovernment Nika riots of 532. Justinian then commissioned a new church and, in response to his dictum that Aya Sofya be the grandest place of worship ever built—far greater than the temples whose columns were incorporated in the church—his master architects devised a magnificent dome. New architectural rules were made up as the builders went along, though not all were foolproof, since the dome collapsed during an earthquake just two years after the church was completed. The church stood a shell until a new architect built a steeper dome, and the aged Justinian finally reopened the church on Christmas Eve 563. Subsequent repairs and such structural innovations as flying buttresses ensured the dome remained firmly in place, making it the prominent fixture it is on the Istanbul skyline to this day. Over the centuries Hagia Sophia has survived additional earthquakes, looting Crusaders, and the conquest of the city by Mehmet the Conqueror in 1453.
Mehmet II famously sprinkled dirt on his head before entering the church after the conquest as a sign of humility. His first order was for Hagia Sofya to be turned into a mosque and, in keeping with the Islamic proscription against figural images, mosaics were plastered over. Successive sultans added the four minarets, mihrab (prayer niche), and minbar (pulpit for the imam) that visitors see today, as well as the large black medallions inscribed in Arabic with the names of Allah, Muhammad, and the early caliphs. In 1935, Atatürk turned Hagia Sophia into a museum and a project of restoration, including the uncovering of mosaics, began.
Recent restoration efforts have, among other things, uncovered the large, beautifully preserved mosaic of a seraph, or six-winged angel, in the northeast pendentive of the dome, which had been plastered over 160 years earlier. The 9th-century mosaic of the Virgin and Child in the apse is also quite impressive: though it looks tiny, it is actually 16 feet high. To the right of the Virgin is the archangel Gabriel, while Michael, on the left, is almost totally lost.
The upstairs galleries are where the most intricate of the mosaics are to be found. At the far end of the south gallery are several imperial portraits, including, on the left, the Empress Zoe, whose husband's face and name were clearly changed as she went through three of them. On the right is Emperor John Comnenus II with his Hungarian wife Irene and their son, Alexius, on the perpendicular wall. Also in the upper level is the great 13th-century Deesis mosaic of Christ flanked by the Virgin and John the Baptist, breathing the life of the early Renaissance that Byzantine artists would carry west to Italy after the fall of the city to the Turks—note how the shadows match the true light source to the left. The central gallery was used by female worshippers. The north gallery is famous for its graffiti, ranging from Nordic runes to a complete Byzantine galley under sail. On your way out of the church, through the "vestibule of the warriors," a mirror reminds you to look back at the mosaic of Justinian and Constantine presenting Hagia Sophia and Constantinople, respectively, to the Virgin Mary.
Aya Sofya Sq., Istanbul, Turkey