A souterrain is an underground stone-lined passage or chamber, typically built during the early medieval period and associated with nearby settlements, used variously for storage, refuge, or both. At this particular spot, the evidence for one is almost entirely absent from the surface, which is itself a quietly interesting fact: the archaeology here exists, if it exists at all, entirely out of sight.

What little is known comes from an observation made by a researcher named Bowman in 1934, who recorded that depressions in the centre and south-west of the enclosure suggested the presence of souterrains below. The enclosure in question is a ringfort, one of the circular earthen or stone-walled farmsteads that were built across Ireland in their thousands during the early medieval period, roughly between the fifth and twelfth centuries. Souterrains are frequently found within or adjacent to ringforts, and the pairing here would be entirely consistent with that pattern. But Bowman's depressions are the sum total of the physical record. No visible surface trace has been identified since.