Hagia Sophia is too complex for Erdoğan's cleansing

“Solomon, I have outdone thee.” So remarked Justinian, the Roman emperor who commissioned Hagia Sophia, the great cathedral at the heart of Constantinople, now Istanbul. Throughout its history it has been a source of wonder and debate. Now, the decision by the Turkish president, Recep Tayyip Erdoğan, to turn it back into a mosque has reawakened many of the historical and religious ghosts that haunt its sublime spaces.

Completed in 537, Hagia Sophia was at once the culminating architectural achievement of late antiquity and the first Byzantine masterpiece. Most remarkable was the huge dome at the heart of the building. “It seems not to be founded on solid masonry, but to be suspended from heaven,” wrote the great historian Procopius. A millennium later, the Ottoman historian Tursun Beg was equally awestruck: “What a dome, that vies in rank with the nine spheres of heaven!”

Beneath the dome are 40 windows through which sunlight suffuses the interior, illuminating gold mosaics and conjuring, for believers and non-believers alike, a sense of ineffable mystery.

Hagia Sophia was the seat of the Orthodox patriarch of Constantinople, and the spiritual heart of Byzantium. After the city was captured by the Ottomans, in 1453, Constantinople became Istanbul and Hagia Sofia a mosque, Ayasofya. In 1935, under Mustafa Kemal Atatürk, it was turned into a museum.

The stones, pillars and mosaics of Hagia Sophia embody the complexity of Turkish and European history, of the Christian and Islamic traditions. Its very existence is a rebuke to Erdoğan’s attempt to cleanse history of that complexity, and to conjure a singular, mythical past.

• Kenan Malik is an Observer columnist