The ground above it looks like ground. Nothing breaks the surface. The only reason we know to look is a small open circle inked onto the first edition of the Ordnance Survey six-inch map, accompanied by the neat, matter-of-fact label "Subterraneous Passage".

The passage is a souterrain, a type of man-made underground structure, usually stone-lined, that was commonly built in early medieval Ireland as a place of refuge, storage, or concealment. This one sits within a ringfort, a circular enclosed settlement of the same period, defined by an earthen bank or banks and typically home to a farming family of some status. The pairing is not unusual; souterrains are frequently found inside ringforts, tucked beneath the domestic space of the enclosure. What is notable here is the completeness of the disappearance. At the time the first edition OS map was surveyed in the nineteenth century, enough of the feature was evident to be recorded and named. Since then, whatever trace remained at the surface has gone, leaving only the cartographic note as evidence that something was once there to find.