That gap, half a metre high and not quite a metre across, is the current way into an early medieval souterrain, an underground stone-lined passage or chamber typically used for storage, refuge, or both, that has been sitting quietly in rough pasture here for well over a thousand years. The debris piled both inside the chamber and on top of the structure outside suggests someone excavated it deliberately at some point, though when and why remains unknown.

The structure is roughly L-shaped in plan. Its main element is a single D-shaped chamber, running north to south, measuring 2.45 metres long and 1.3 metres wide, with a maximum height of 1.5 metres. Three roofing slabs span the top, and the upper two or three courses of the drystone walls are corbelled inwards, a technique where successive stone layers are stepped gradually toward the centre, narrowing the chamber at roof level to around 0.9 metres. At the north end of the east wall, a creepway, a deliberately tight connecting passage designed so that only one person at a time could pass through it, leads into a second section running east to west. This passage is at least four metres long, its walls built from upright slabs overlain with drystone courses. The eastern end is choked with accumulated fill, which has raised the passage floor on a slope toward that end. A small hole is visible in the roof at this point, though it is unclear whether it marks the original entrance or whether the passage continues further eastward, still buried. That uncertainty is part of what gives the site its particular quality: it remains genuinely unresolved, a structure not fully understood even by those who have studied it closely. The description of the souterrain was first recorded in J. Cuppage's 1986 Dingle Peninsula archaeological survey of the Corca Dhuibhne region.