A souterrain, which is a stone-lined or rock-cut tunnel typically built during the early Christian period in Ireland to serve as a place of refuge, storage, or concealment, once lay undisturbed beneath this agricultural land. Then the plough broke through, and the structure collapsed into itself.

The detail is a small but telling one. Souterrains across Ireland have survived for well over a thousand years, often because they happened to lie under pasture or bog, undisturbed by heavy machinery. In tillage ground, the repeated cycle of deep ploughing poses a particular threat to any buried void. At Coolmore, that threat became reality. The collapse was noted as recent at the time the site was recorded, leaving the souterrain inaccessible and its extent, condition, and construction unknown beyond the bare fact of its existence.