The entrance to a souterrain, an underground passage or chamber typically used in early medieval Ireland for storage or refuge, was noted here by a researcher named Henry as far back as 1957, though the dense vegetation that has since taken hold makes it impossible to verify from the surface today.

The structure itself is a caher, the Irish term for a stone-walled ringfort, as distinct from the earthen-banked raths more commonly associated with early medieval settlement across the country. This one sits in level pasture on An Seanchnoc in County Kerry, a modest and roughly circular enclosure measuring around 17 metres north to south and 13 metres east to west. Its wall, about 1.5 metres wide, was built with a rubble core sandwiched between two faces of drystone masonry, a technique that gave it solidity without mortar. Time has not been especially kind to it; the wall survives to no more than 1.1 metres at its highest point. The entrance, less than a metre wide and set into the south-eastern arc of the wall, is still legible, its sides flanked by upright stone slabs that reach nearly a metre in height, giving it a quiet formality that the rest of the crumbling circuit no longer quite manages.