According to tradition, St. Patrick founded a monastic settlement on the nearby Saint’s Island in the fifth century, installing Dabheoc as its first abbot. The monks’ primary role was to minister to the steady stream of pilgrims who came to experience St. Patrick’s Purgatory, a cave where medieval believers thought they could glimpse the afterlife. Some historians suggest the original cave was actually on Saint’s Island before the pilgrimage relocated to Station Island, though the exact sequence of events remains murky.

During the Middle Ages, the Lough Derg pilgrimage achieved fame across Europe, spawning an extensive body of literature and attracting believers from far and wide. This popularity also drew fierce opposition from various authorities who viewed the site with suspicion. In 1494, a Dutch Augustinian denounced it as a sham to Pope Alexander V, who ordered its closure. Three years later, the cave was supposedly demolished on St. Patrick’s Day by papal authority, though the Annals of Ulster intriguingly noted that the destroyed purgatory wasn’t the real one; perhaps the Augustinian canons had conveniently shut down a ‘false’ cave, allowing the original pilgrimage to continue. The Protestant authorities made a more thorough attempt at destruction in 1632, ordering all buildings on both islands demolished and the masonry cast into the lake due to what they called the pilgrimage’s ‘extremely abusive and superstitious’ nature.

Despite centuries of suppression, including another closure in the 1780s ostensibly for safety concerns about overcrowding, the pilgrimage proved remarkably resilient. The underground purgatory element disappeared after the 1632 demolitions, replaced by an above-ground building shown on maps from 1666. Today, after two centuries of continuous development, little remains of the island’s medieval structures save for a few fragments: a cross shaft, a broken cross head, and a small font. The so-called penal beds visible today are relatively recent additions, and even the location of the original cave can only be guessed at. Yet St. Patrick’s Purgatory continues to draw thousands of pilgrims each summer, maintaining a tradition that has survived papal prohibitions, physical destruction, and the passage of fifteen hundred years.