That detail alone sets the souterrain at Cloghalahard apart from the more familiar examples of its type. A souterrain is an artificial underground passage or chamber, typically built during the early medieval period in Ireland, constructed from drystone walling and used variously for storage, refuge, or ventilation of nearby settlement sites. Most follow a reasonably predictable template. This one does not.

The chamber at Cloghalahard runs east to west, stretching roughly seven metres in length and 1.7 metres across, its walls laid without mortar in the drystone tradition. It sits immediately to the east of what may be a cashel, a type of stone-walled enclosure associated with early medieval farmsteads, though the relationship between the two structures has not been fully resolved. A small alcove extends from the western end of the southern wall, measuring about 1.5 metres deep and 0.7 metres wide. Archaeologists have noted that there is no evidence to suggest this recess functions as a creep, which is the term for a low connecting passage that links one souterrain chamber to another, typically designed to be narrow enough to impede intruders. What the alcove was actually for remains unclear. More puzzling still is the well sunk into the floor of the chamber, positioned a short distance east of the entrance. Redington, writing in 1912, recorded the feature, but the question of whether the well was part of the original design or a later addition is not answered by the surviving evidence.

Access to the chamber is now made via a flight of concrete steps installed at its western end, a practical intervention that at least confirms the structure has been recognised and stabilised at some point in the relatively recent past.