This is what archaeologists call a souterrain, an artificial underground structure built from dry-stacked stone without mortar, typically associated with early medieval settlement and used variously for storage, refuge, or both. What gives this particular example its quiet peculiarity is the junction between its two chambers: a drop-hole creep, a deliberately narrow constriction measuring roughly eighty centimetres by forty-five, through which a person must squeeze and descend. Anyone being pursued would find it a serious obstacle. Anyone who knew the way would find it navigable.

The southern chamber, running north to south and partially tucked beneath the bank of the enclosing rath, a roughly circular earthwork enclosure characteristic of early medieval Ireland, is now entered through a breach in its western wall, well away from the original entrance. The northern chamber, which runs east to west and reaches nearly ten metres in length, appears to have been where people originally came in; a large blocking stone positioned near the creep junction suggests a deliberate closing of that access point at some stage. Part of this northern chamber now lies beneath a road, which has both preserved it and complicated any full understanding of it. When McCaffrey catalogued the site in 1952, he recorded it as a standalone souterrain, unconnected to any enclosure. Later survey work corrected that, establishing clearly that it sits within the southern sector of an associated rath, a relationship that changes how the structure should be read: not an isolated oddity but a deliberate underground feature of a larger defended settlement.