On a gently rising hillside at Rathduff, near Emper, the remains of a roughly circular enclosure about twenty-five metres across sit in open grassland. The enclosure's earthen bank has been largely levelled along its northeastern to south-southeastern arc, but what makes the site genuinely odd is not what survives above ground. Beneath the interior, an underground passage, or souterrain, a type of dry-stone tunnel common in early medieval Ireland and often associated with settlement or storage, has been cut into the earth. Built into the wall of that souterrain is a long stone carrying prehistoric rock art, abstract carvings whose origins predate the tunnel itself by a very considerable margin.

The presence of decorated prehistoric stonework reused in a later structure is not without parallel in Ireland, but it is always a striking thing to encounter. The rock art stone was clearly not carved for the souterrain; it was taken from somewhere else, or repurposed from an earlier context on the same ground, and incorporated into the passage wall by whoever constructed it. The souterrain's entrance opens from the northern side of the interior. At the south-southeast, three stones set on edge form a revetment against the inner face of the bank, and a large upright flagstone nearby may represent one side of an original entrance to the enclosure itself. Just twenty-five metres to the southeast lies a flat cemetery, suggesting the site sits within a broader landscape of long and layered use. The hill offers open views to the east, south, and southwest, a feature that would have made it a meaningful place across several different periods of occupation.