It is not dramatic from above, just a shallow depression in the ground, roughly five metres long, a little over a metre wide, and barely more than half a metre deep at the surface. But that sunken trace marks the roof line of a souterrain, an underground passage or chamber built during the early medieval period, typically from dry-laid stone, and used for storage, refuge, or both.

The souterrain sits within the northern half of a rath, the circular earthwork enclosure that was the standard form of a defended farmstead in early medieval Ireland, broadly from the sixth to the twelfth centuries. The combination is not unusual in itself; souterrains are frequently found inside raths across the country. What is notable here is a brief mention in the Minutes of the Co. Kerry Field Club from 1941, which records the structure as being 'well-built'. That phrasing, coming from a field observation rather than a formal excavation, suggests the stonework was still coherent enough at that point to make an impression on whoever examined it, even though the passage had long since been sealed or collapsed at the surface.