A clochaán, or clochán, is a corbelled stone structure built without mortar, each course of stones projecting slightly inward over the one below until the opening closes at the top; the technique is ancient, and on this island it was refined to an extraordinary degree. What sets this particular structure apart from its neighbours is the detail hidden in plain sight: a discontinuous spiral of stone offsets wraps around the exterior wall, projecting slabs step outward from the inner face, and carved into the innermost lintel above the doorway are two superimposed triangles and an equal-armed cross with T-shaped terminals. These are not decorative afterthoughts. They were cut into stone on a sea-lashed rock twelve kilometres off the Kerry coast, presumably by monks who had chosen one of the least hospitable places in Europe to pursue a life of prayer.

The doorway itself rewards close attention. It stands 1.55 metres high and tapers as it rises, narrowing from 0.9 metres at the base to 0.63 metres just under the lintel head, a shape that would have made entry a deliberate, slightly awkward act. Above the doorway on the exterior wall, several quartz stones are set into the face in the form of a Latin cross. Inside, four small lintelled openings admit light at varying heights; one sits relatively low at 1.6 metres above floor level, while three others are placed at around three metres. Four shallow wall-niches are cut into the lower interior, averaging roughly 26 by 48 centimetres and about 44 centimetres deep. Ten stone slabs project from the inner wall surface beneath the upper windows, and scholars including Liam de Paor and Françoise Henry, writing in the 1950s, proposed that these served a constructional purpose during the building of the dome rather than any liturgical one. A later and more unexpected detail comes from the antiquary John Windele, who recorded a local tradition that lighthouse workmen once found a stone coffin containing a skeleton inside this very structure, though the circumstances and date of that discovery remain obscure.