The Hagia Sophia (Greek for “Holy Wisdom”) was a Greek Orthodox cathedral from 537 to 1453. When the Ottoman Empire conquered Constantinople the church was converted into a mosque. Then in 1935 it was converted into a museum.
No musical performances are allowed in the Hagia Sophia. However, researchers from Stanford have modeled the acoustics of the space in order to simulate what worship would have sounded like when it was a medieval cathedral. The researchers recorded a virtual performance by synthesizing the acoustics of the building. Not only did they post-process the sound to give the singers the sound of being in the Hagia Sophia, they first gave the singers real-time feedback so they would sing as if they were there.