The souterrain, an underground tunnel or chamber typically built during the early medieval period and associated with nearby settlements or fortified enclosures, lies sealed. The landowner confirmed it was closed up many years ago, and the former point of entry is all that remains visible to mark what once led underground.

The ringfort in whose southern half this souterrain sits is recorded as 'Uainmore', a name that appears on the third edition of the Ordnance Survey six-inch map, surveyed between 1915 and 1916. Ringforts, the circular enclosed farmsteads that dot the Irish countryside in their thousands, were built primarily between the sixth and tenth centuries, and souterrains were frequently incorporated into them. Their precise function is still debated; they may have served as refuges, as cool storage for dairy produce, or as escape routes in times of danger. At Carrownakib, the construction was of stone, which is consistent with the geology of Connacht, where dry-stone building traditions run deep. Beyond those bare details, the passage keeps its own counsel.