It does not look like much at first glance, but the arrangement may be the collapsed roof of a souterrain, an underground stone-lined passage or chamber built during the early medieval period, typically used for food storage, refuge, or both.

The stones sit within a cashel, which is a circular enclosure defined by a dry-stone wall, the Irish equivalent of a fortified farmstead from roughly the early Christian period onwards. Cashels are relatively common across the west of Ireland, but the possible souterrain here adds a layer of complexity to the site. Souterrains were carefully constructed, often running for several metres underground, and their roofing stones, when the structure eventually gives way, tend to collapse inward and settle into the kind of irregular but concentrated spread visible at Polldonoghoe. The qualification matters, though: the evidence as it stands points to a possible souterrain rather than a confirmed one, and without excavation the question remains open.