Not cramped, hunched spaces, but chambers tall enough to stand upright in, connected by passages of dry-laid stone and roofed with heavy slabs. The extraordinary thing is that nobody knows precisely where they are. The ground above gives nothing away, and the souterrain, as such an underground stone structure is known, leaves no visible mark on the surface of the enclosure that contains it.

Souterrains are a recurring feature of early medieval Irish settlement, typically associated with raths, the circular earthwork enclosures, also called ringforts, that were the most common form of farmstead in Ireland from roughly the sixth to the twelfth century. They were built without mortar, the stones carefully selected and stacked so that the structure held its own weight, and they are thought to have served variously as storage spaces, refuges, or places of concealment. The one at Gorteen is recorded as having at least three chambers, with a partly paved floor as well as the stone-slab roof, suggesting some care in its construction. What survives, however, is known primarily through local information rather than any formal excavation or survey. Its relationship to the rath above it, including whereabouts within that enclosure it actually lies, remains unresolved.