A souterrain, as these stone-lined tunnels are known, is a type of subterranean chamber built during the early medieval period, typically within or beside a ringfort, and used variously for storage, refuge, or both. This one now presents to the world only a single exposed lintel, a flat capstone roughly 90 centimetres wide, resting on drystone walling above an opening barely wide enough to admit a person sideways. The gap between the clay fill and the underside of the lintel has narrowed to about 25 centimetres. Whatever lies beyond is, for now, sealed.

The Ordnance Survey's six-inch map of 1842 marked the feature and named it plainly as a 'cave', which tells us it was still known locally and presumably still accessible at that time. By the 1915 edition it had vanished from the cartographic record entirely. The antiquarian Thomas Johnson Westropp visited sometime before his 1911 publication and left behind the most complete account we have. He measured the passage at just over ten and a half metres in length, with an interior wide enough to stand upright towards the far end, rising from roughly 86 centimetres at the entrance to nearly two metres inside. He noted twelve lintels spanning the roof, a projecting cornice along the walls, a shallow side recess, and an ambiguous void at the terminal end that opened beneath the roof but did not appear to lead anywhere further. It was, by his account, a well-made and relatively spacious example of its kind. The passage he walked no longer admits visitors; the estimated four metres still traceable from the surface represent perhaps a third of what Westropp recorded, with the rest presumed collapsed or entirely buried beneath the ringfort's interior.