That small collapse is the only point of entry for light and line of sight, offering just enough of a glimpse to confirm what lies beneath: a drystone-built rectangular souterrain, the kind of subterranean chamber that appears at early medieval Irish settlements and is thought to have served as storage, refuge, or both.

The passage runs east to west and measures 9.3 metres in length, 1.5 metres wide, and 1.5 metres high, proportions that would have allowed a person to move through it in a crouch. It sits inside a cashel, a type of stone-walled enclosure used as a farmstead or defended residence during the early medieval period, built without mortar in the drystone tradition common across the west of Ireland. The cashel itself is recorded separately, and the souterrain appears to have been an integral part of that original complex rather than a later addition. The collapsed lintel at the western end suggests the structure has endured considerable time underground, and while the passage remains inaccessible, the breach at least confirms that the interior survives in some form.