This is a souterrain, a type of man-made underground structure built during the early medieval period, typically of dry-stone construction and roofed with large flat lintels laid across the walls. They are found across Ireland in association with raths, the circular earthen enclosures, sometimes called ringforts, that served as farmsteads for wealthy families between roughly the sixth and twelfth centuries. Their exact purpose remains a matter of debate among archaeologists, though cold storage, refuge, and ventilation have all been proposed.

This particular souterrain lies within the north-western quadrant of a rath recorded separately in the archaeological record. The passage runs north to south, measures between four and four and a half metres in length and approximately 1.2 metres in width, and is built using dry-stone walling topped with lintels. The southern access point has been blocked with stones at some point, leaving the structure effectively closed. To the south of the visible passage, a depression roughly four metres long may mark a section that has collapsed, suggesting the original structure could have extended further than what now survives above ground.