This is a souterrain, an underground passage or chamber built from stone, typically associated with early medieval ringforts and cashels in Ireland. Their precise purpose is still debated, though most archaeologists favour some combination of storage, refuge, and ventilation. What makes this one quietly arresting is its position: not tucked against a wall or hidden at the margins, but placed at the very centre of the cashel.

The cashel itself, a type of stone-walled enclosure characteristic of early medieval Ireland, is recorded separately and provides the immediate context for the souterrain. The underground feature measures 7.8 metres in total length and bends eastward, coming to within 1.5 metres of the cashel's enclosing wall before stopping short. That proximity to the wall is suggestive, possibly deliberate, offering either a concealed exit or simply making use of the structural logic of the enclosure. The stone flags that have been exposed at the surface give some indication of the care that went into its construction, even if the full extent of what lies beneath remains unexcavated or undocumented in detail.