Hagia Sophia

“Nestor the Chronicler reported that travelers to the Hagia Sophia in 987 AD were awestruck with the structure remarking “we knew not whether we were in heaven or on earth…for on earth there is no such splendor or such beauty, and we are at a loss how to describe it. We only know that God dwells there among men…”

From this paper by Robert Ousterhout : https://www.medievalists.net/2021/05/justinians-hagia-sophia/