Patrick supposedly installed Dabheoc as the first abbot here, establishing a religious community that would later become crucial to one of medieval Europe’s most famous pilgrimage sites. The original monastery likely stood on this island before transforming into an Augustinian priory dependent on Armagh’s Abbey of SS Peter and Paul during the 1130s. By the late sixteenth century, the priory had been suppressed and abandoned, though its primary purpose had long been ministering to pilgrims visiting St. Patrick’s Purgatory, a cave that drew believers from across the continent. Some scholars suggest the famous cave originally existed on Saint’s Island itself before the pilgrimage relocated to nearby Station Island, where it continues today.

The archaeological remains on Saint’s Island paint a picture of its monastic past, though time and vegetation have obscured many details. The western half of an earthen enclosure survives, measuring about 20 metres in diameter with an exterior fosse up to 1.5 metres wide. A rectangular graveyard, enclosed by drystone walls and measuring 27 by 22.5 metres, appears to have destroyed the enclosure’s eastern portion. At the graveyard’s centre, an irregular pile of rubble holds graveslabs placed without apparent order, possibly representing the foundations of a rectangular structure shown on old Ordnance Survey maps. A 44-metre pathway marked by two lines of grass-covered stones leads northeast to another rectangular foundation, built of drystone with walls up to 1.15 metres wide and 0.95 metres high.

The pilgrimage route itself tells a story of medieval devotion, with an ancient roadway connecting the village of Pettigo to Lough Derg’s southwestern shore. This path passes significant sites including Rathnacross ringfort and Templecarn church and burial ground before reaching a point where a wooden bridge once connected the mainland to Saint’s Island; natural boulders projecting from the lake may be the remnants of its supports. Around the lake, various features speak to centuries of religious practice: St. Brigid’s Chair, a natural L-shaped stone on the southeastern shore; St. Dabheoc’s Seat, once consisting of a stone seat before a grave-like opening on a southern hill, though forestry has since claimed the site. Additional archaeological features on the island include what appears to be part of another circular enclosure and evidence of an old quay at the northeastern end, suggesting the practical infrastructure that supported this once-thriving religious community.