The Cave of the Apocalypse is about halfway up the mountain on the island of Patmos, Greece. This grotto is believed to mark the spot where John of Patmos received his visions that he recorded in the Book of Revelation. UNESCO has declared it a World Heritage site.[1]
Mosaic above the entrance to the Cave of the Apocalypse, picturing John of Patmos (on the right) and his disciple Prochoros, who transfers John's visions into writing.