Partially blocked by stone infilling, it is easy to dismiss, yet it marks the entrance to something considerably older and more deliberate: a souterrain, an underground stone-lined passage or chamber built, typically in the early medieval period, for storage or refuge beneath a defended settlement.

The rath itself, a circular earthwork enclosure of the kind used as a farmstead by early Irish families, provides the context. In its west-north-western interior, the partially visible opening retains traces of its original construction: the stone lining of the passage walls and, still partly in place, a lintel slab, one of the flat stones that would have formed the roof of the underground structure. Souterrains were often built with considerable skill, their corbelled or lintelled roofs engineered to bear the weight of the earth above, and even this fragmentary survival gives a sense of that original ambition. The stone infilling that now obscures much of the opening may reflect deliberate backfilling at some point, or simply centuries of collapse and accumulation.