Then, in 1999, the ground simply gave way, opening a metre-wide hole into something that had been sealed beneath the pasture all along. What the collapse revealed was a souterrain, an underground structure of the kind built throughout early medieval Ireland, typically cut or constructed beneath farmsteads as places of refuge, storage, or concealment. This one turned out to be unusually elaborate.

The structure runs through five earth-cut chambers connected by creepways, the low, narrow passages that force anyone passing through to crouch or crawl, presumably slowing down anyone who was not supposed to be there. The chambers vary in plan and proportion; some are roughly rectangular, others bulge into oval shapes at their ends, and the final chamber narrows and slopes upward into a curving extension. Heights throughout hover below a metre, so none of it was designed for comfort. What is particularly striking is the number of blocked-up construction shafts, vertical openings used during the building process and then sealed once the underground work was complete. Chamber 2 alone contains two of them, and every chamber has at least one. A small annexe off the first chamber even appears to have a possible air-vent in its corner. The whole system sits on a north-facing slope overlooking a stream valley, a setting that would have placed it discreetly below the activity of whatever settlement once occupied the ground above.

Because the site lies in private pasture and access has not been formalised, there is no straightforward way to visit the interior. The collapse that first opened the souterrain was the only unintended entry point, and much of that first chamber remains choked with the debris of fallen earth and stone.