The entrance is barely forty centimetres high and just over a metre wide, a gap that requires a person to get very low to the ground before the passage opens slightly, running west-northwest for nearly three metres before turning and continuing for another four, where fallen stone blocks the way. This is a souterrain, an underground structure built in early medieval Ireland typically for storage, refuge, or both, its drystone walls corbelled inward as they rise and roofed with large flat lintels, the whole thing assembled with considerable care by someone who knew what they were doing.

Scariff Island lies five kilometres south-west of Hog's Head in County Kerry, on the northern side of the Kenmare Bay entrance. The ecclesiastical site it contains is reached by a path climbing from the landing place at Cuas na Naomh, which translates roughly as the Cove of the Saints, on the island's north-eastern shore. At the top, a terraced oval enclosure once held an oratory and a burial ground, and a nineteenth-century house was later built within the same space, an arrangement that speaks to how persistently people have returned to this small patch of ground. The souterrain sits just outside the south-western edge of that enclosure, built into the hillside slope as if deliberately placed at the margin of the sacred space rather than within it. Whether it served the early monastic community as a cool store for provisions, or offered concealment during periods of threat, the structure's relationship to the enclosure beside it remains a matter of inference rather than record.