From Aleteia:
The Cave of the Apocalypse lies along the road connecting Skala to Chóra on the Greek island of Patmos. For centuries, Christians have identified this small grotto as the place where John the Apostle received the visions recorded in the Book of Revelation.
According to early Christian tradition, John was sent to Patmos during the reign of the Roman emperor Domitian. Exile was a standard punishment within the empire, particularly for those suspected of engaging in prophecy, which Roman authorities viewed as a political risk. The island functioned as a place of confinement, and John’s presence there reflected the broader pressure faced by early Christian communities.