Hagia Sophia, from basilica to mosque

In front of you stands the building that for almost a thousand years was the largest church in Christendom. From outside, a mass of pinkish walls and buttresses, you'd barely guess what it hides within: a dome that seems to float on a ring of light.

1Five years for a miracle

Two earlier churches stood on this site. The second burned down during the Nika riot of 532. Just weeks later, Justinian ordered a new one and gave the design to two scholars, Anthemius of Tralles and Isidore of Miletus, who were mathematicians more than architects. The church was consecrated in December 537. In 558 an earthquake brought down part of the dome, which was rebuilt higher: the one you still see today.

2The change of 1453

On 29 May 1453, the day of the Ottoman conquest, Mehmed II entered the church and turned it into a mosque. Over the years minarets, a mihrab and the great calligraphic roundels were added, and outside, the mausoleums of sultans. The mosaics were covered over rather than destroyed, which is why so many have survived.

In 1934 a decree of the Republic made it a museum; in 2020 a ruling by the Council of State returned it to worship as a mosque.

Today it is visited as a working mosque, with the dress code and prayer-time closures that implies.

3What to look for

• The buttresses: the massive props along the sides were added at different times to stop the dome spreading.
• The four minarets, each different because they were built at different times.
• The Ottoman mausoleums by the south wall, with their small domes.