Saint Patrick is one of the most fascinating figures in Irish history. As with many saints, the stories surrounding him have been told for centuries altered and embellished countless times along the way. It’s tough to separate fact from fiction, but one thing’s certain: he didn’t drive the snakes out of Ireland.

Somewhere on a small Irish island, though, there’s said to be a portal to the gates of Hell. Saint Patrick’s involvement with this grisly gateway, and the monastery built above it, dates back quite a long time. Lough Derg is home to St. Patrick’s Purgatory and one of the most grueling Christian pilgrimages on the planet. It’s said that, on this small, unassuming island, St. Patrick was visited by Jesus himself. He took the Saint to a secluded spot where he was subjected to a first-hand glimpse of the underworld. Needless to say, such images spurred Saint Patrick and those who supported him to new levels of piety. A monastery was constructed on the island, and while there’s no historical evidence that the Saint was ever here himself, it bears his name. While casual visitors are not generally allowed on the island, yearly pilgrimage to the site continues to this day where devout worshippers come in droves to take a three-day sojourn of contemplation through the holy site.