Cave of the Apocalypse

The Cave of the Apocalypse is located approximately halfway up the mountain on the Aegean island of Patmos, along the road between the villages of Chóra and Skala. This grotto marks the spot where St. John of Patmos received his visions that he recorded in the Book of Revelation. It became a location of Christian pilgrimage and is recognized as a Greek Orthodox Church to this day. In 1999, UNESCO declared the cave a joint World Heritage Site, as one of the most sacred sites of Christianity.

Source: Wikipedia