It is a souterrain, a type of man-made underground structure built during the early medieval period in Ireland, typically comprising stone-lined tunnels or chambers dug into the earth. These features are found across the country in considerable numbers, yet each one carries its own particular silence. They were used variously for storage, refuge, or ventilation for surface settlements, and the fact that so many survive at all, even as grassed-over humps in a field, speaks to how thoroughly they were built.

Bawnaglanna itself is a small rural townland in Kerry, a county that contains a remarkable density of early medieval and prehistoric remains, from ring forts to ogham stones to promontory forts along the Atlantic edge. Souterrains are frequently found in association with ring forts, the circular earthwork enclosures that once served as farmsteads for early Irish families, and it is likely that this example once formed part of such a settlement. Beyond its classification and location, the specific details of this particular souterrain, its dimensions, its construction, its current condition, remain at present unavailable in any publicly accessible form.