No hollow in the ground, no tell-tale depression in the grass, no exposed stonework gives it away. It is, by all accounts, simply there, buried and invisible.

The structure is a souterrain, a type of man-made underground passage or chamber commonly associated with early medieval ringforts in Ireland. These features were typically cut into subsoil or built from stone, and they served various purposes depending on the site, from storage and refuge to ventilation for adjacent dwellings. In this case, the souterrain lies within a ringfort recorded separately in the archaeological record, a circular enclosure whose earthen banks would once have defined a farmstead or settlement. The Ordnance Survey Name Books, compiled in the nineteenth century as part of Ireland's first systematic mapping project, noted the presence of a large cave in the interior of this ringfort, which is how the feature first entered the written record. That description, brief as it is, remains the principal source of what is known about it.