This is a souterrain, a type of dry-stone underground passage or chamber associated with early medieval Irish settlements, typically built for storage, refuge, or concealment. At just over 2.7 metres long, a metre wide, and 1.2 metres high, it is a tight, purposeful space. Its walls are corbelled, meaning the stones are layered so that each course projects slightly inward over the one below, creating a self-supporting structure without mortar. At the southern end, what may be a creep, a low connecting passage requiring a person to crawl, extends at floor level, hinting at a more complex layout than the visible section alone suggests.

The antiquarian Thomas Johnson Westropp visited and recorded the site in 1901, noting an additional east-west section that he believed formed a single L-shaped souterrain together with the north-south passage. Whether or not that interpretation holds, the structure sits to the south-west of the centre of Cahermoyle cashel, a ringfort-type enclosure typical of early medieval Ireland, where such underground passages were sometimes integrated into the defensive or domestic arrangements of a settlement. When the souterrain was inspected again in 1999, some nine decades after Westropp's account, it had acquired a new occupant. A badger had taken up residence inside, which perhaps says something about the enduring practicality of corbelled stonework as shelter.