The conquest of Constantinople by Sultan Mehmed II on May 29, 1453 CE saw the Hagia Sophia pillaged as the invaders believed it to contain the greatest treasures of the city, and became as a result the focal point of the siege. Unfortunately the church was being used as a refuge for those unable to contribute in the city’s defense, and congregants who had gone to the basilica to pray. Those not slaughtered as the invaders battered their way in, were enslaved and divided amongst the Ottomans. Immediately after the conquest the Hagia Sophia was repaired and converted into a mosque. With the first Friday prayer – held on June 1, 1453 – it became the first imperial mosque of Istanbul.
Over the centuries the building would continue to morph and grow thanks to proclamations like the imperial charters of 1520 and 1547 which allowed for shops and parts of the Grand Bazaar and other markets to be added to the foundation, or the additions of minarets and a Sadirvan for ritual ablutions.
A series of tombs located around the rear of the building were added over time for the Ottoman princes and the immediate royal families.
The interior also went through multiple renovations as the ruling Ottomans left their mark upon the building – Sultan Suleiman the Magnificent for example brought back two colossal candlesticks from his conquest of Hungary (ca. 1521) and had them placed to either side of the mihrab. The last of the Ottoman renovations (performed between 1847 and 1849) which saw the chandeliers and the giant medallions installed – inscribed with the names of Allah, the Prophet Muhammad, the first four caliphs, and Mohammad’s two grandchildren – were for the first time done so under the supervision of foreigners; the Swiss-Italian architect brothers Gaspare and Giuseppe Fossati.