There is no hollow, no depression, no marker of any kind at ground level. The only reason anyone knows it exists is because people locally have passed the knowledge down since its discovery around 1940.\n\nWhat lies here is a souterrain, an underground passage or chamber typically constructed during the early medieval period in Ireland, often associated with nearby settlement sites. Souterrains were built from stone-lined or rock-cut passages and served various purposes, most likely as places of refuge or cool storage for food. The Kiltillahan example sits on a north-west-facing slope, with a stream roughly a hundred metres to the north-west, a setting consistent with the kind of sheltered, watered ground that early communities favoured. How it was discovered around 1940 is not recorded, but the fact that local memory has preserved awareness of it for decades, even as the land returned to ordinary agricultural use, says something about how thoroughly these features can disappear into the landscape while still persisting in conversation.