What they broke into instead was something far older: a souterrain, an underground structure of the kind built in early medieval Ireland, typically consisting of stone-lined passages used for storage, refuge, or both. The Kerry Sentinel reported the discovery on 30 January 1892. By then, it had apparently already been destroyed.

The structure lay only a few feet below the surface, its roof formed from large flat lintels laid across drystone walls, the masonry described as well-built. Inside were several passages. The walls showed traces of soot, and the floor yielded oyster and periwinkle shells, ash, charcoal, and pieces of iron. These are the kinds of finds that suggest repeated use over time, people sheltering, cooking, or storing food in a space that was deliberately hidden from view. The site was never marked on Ordnance Survey maps, which means it existed only in local memory before the railway came and erased it entirely. There is no monument to visit, no surviving trace in the ground, only the newspaper account of its brief, unfortunate reappearance after centuries underground.