Covered now with wire mesh for safety, the hollow measures roughly 2.9 metres east to west and 2.2 metres north to south, and it marks the sealed entrance to a souterrain, one of those stone-lined underground passages that were constructed throughout early medieval Ireland, most likely for food storage, refuge, or both.

Below the mesh, according to local knowledge, a passage runs for approximately nine metres, narrow enough that an adult would have to crouch to move through it, being around 0.8 metres wide and 0.8 metres high. The passage heads east before reaching a chamber, then turns south. That deliberate change of direction is characteristic of souterrain design, where corners and low ceilings served as practical obstacles to anyone trying to force their way in. The souterrain sits within a rath, the term used for a ringfort, which are the circular earthwork enclosures associated with farming families of the early medieval period, roughly the fifth to twelfth centuries. Kerry has a high density of such sites, and it is not unusual to find a souterrain incorporated into the interior of one, though many have been lost or built over across the centuries.