Set on a south-facing slope at the foot of Knocknakilton mountain, the enclosure is roughly 44.7 metres across, its earthen bank worn low and in places completely vanished, particularly along the eastern quadrant. But cut into the southern interior of this modest rath is a souterrain, an underground stone passage or chamber of the kind that early medieval communities in Ireland used for storage, refuge, or both, and this one has a quiet, particular strangeness to it.

The souterrain is possibly L-shaped in plan, though only one rectangular chamber remains accessible. That chamber runs roughly west-northwest to east-northeast, measuring 4.6 metres long, 1.45 metres wide, and less than a metre high; a cramped, deliberate space. Its walls are built from upright stone slabs topped with drystone masonry, and the upper courses are corbelled inward, narrowing the chamber to just over a metre wide where five roofing slabs sit overhead. At the eastern end of the north wall, a porthole slab, a small opening just 0.45 metres high, once sealed by a stone slab, hints at a passage or further chamber beyond. That passage is now inaccessible. The only way into the accessible chamber today is through a collapse in the south wall, an accident of decay rather than anything intended. Where the original entrance once was remains unclear. J. Cuppage documented the site in the 1986 Dingle Peninsula archaeological survey, and a note from 1945 records that the porthole was formerly closed, suggesting the structure was still being observed and described within living memory of people now old.