Beneath that strip, now sealed under backfilled earth and re-seeded turf, lies a souterrain, a type of underground stone-lined or rock-cut passage built in early medieval Ireland, typically associated with settlement sites and used variously for storage, refuge, or concealment. This one came to light not through excavation but through accident, when the ground simply collapsed during land reclamation works.

What the collapse revealed was a corridor of underground chambers running roughly northeast to southwest for approximately 35 metres. The chambers were barrel-shaped in cross-section, cut from clay rather than built from stone, each about a metre wide and 1.3 metres high, with floors sitting nearly two metres below the surface. They were connected by narrower constrictions known as creep-holes, the kind of tight linking passages that required a person to crouch or crawl between sections, a feature common to souterrains and thought to help control access or provide defensible choke-points. What made this discovery particularly striking was what was found in one of the chambers: a substantial number of human bones. Whether they represent a burial, a later use of the space, or something else entirely, the record does not say. After the find was documented, the chambers were filled in, the ground levelled, and the field returned to agricultural use. The bones were recorded separately. The souterrain itself is now inaccessible, present only as an absence, a linear shadow in the grass that marks where the earth once opened.