The sound of 500 year old choral music in the Hagia Sofia.
“Lost Voices of Hagia Sophiaā€¯ is the first vocal album in the world to be recorded entirely in live virtual acoustics. It brings together art history, music history, performance, and technology to re-create medieval sacred sound in the cathedral of Hagia Sophia as an aural virtual reality.“
Found via this excellent write-up by Kottke.