A souterrain is a man-made underground chamber or passage, typically associated with early medieval settlement in Ireland, often interpreted as a place of refuge, food storage, or both. This one sits beneath a hut site within the cashel, a cashel being a stone-walled enclosure of the kind used to define and defend a farmstead or small settlement. The combination of enclosure, dwelling, and hidden passage layered one atop another suggests a site that was, at some point, deliberately and methodically organised.

The structure itself is modest but well-made. It opens into a chamber roughly 1.5 metres high and 1.5 metres wide, running east to west for about 1.5 metres before bending sharply to run north to south for a further 4.2 metres. That right-angle turn is a common feature of souterrains and is thought to have served a defensive purpose, making it harder for an intruder to move quickly or see clearly in the dark. The walls were built from approximately nine courses of dry-stone, meaning no mortar was used, the stones simply fitted and weighted against one another with considerable skill. Eleven large capstones roof the passage. There is some infill near the entrance, which obscures the original opening and is a reminder that these structures, though built to last, have not always been maintained or fully explored.