It marks the entrance to a souterrain, an underground stone-built passage of early medieval origin, typically used for storage, refuge, or both. The opening is only 24 centimetres high, which means no one has been able to squeeze inside for some considerable time, and the structure sits in quiet inaccessibility on the Kerry hillside, its interior geometry known only from a visit made well over a century ago.

The scholar R. A. S. Macalister recorded the souterrain in 1899, describing two chambers connected by a narrow creepway. The outer chamber, oriented roughly west-south-west to east-north-east, measured 3 metres in length and 1.2 metres in height, enough to sit upright with some comfort. The creepway linking it to the inner chamber was considerably less hospitable, at 60 centimetres high and just 30 centimetres wide, the kind of gap that demands both nerve and a slender frame. Beyond it, the inner chamber opened out again to 3 metres in length and 1.5 metres in width, oriented north-north-east to south-south-west. The whole structure was built in drystone, meaning no mortar, just carefully fitted stones holding one another in place through weight and arrangement alone. Nearby, a clochán, a small dry-stone beehive hut associated with early Christian and pre-Norman settlement, has been largely buried beneath a field clearance cairn, one of those accumulations of removed stones that quietly erase as much as they preserve.