A souterrain is a man-made subterranean structure, typically stone-lined and roofed with large slabs, built during the early medieval period in Ireland as a place of refuge, storage, or concealment. Here, the collapse of whatever once lay beneath has left two hollows pressed into the interior of the rath, the kind of detail that passes easily for ordinary uneven ground unless you know what you are looking for.

The two depressions sit close together within the enclosure. The first, positioned toward the north, is almost V-shaped in plan, measuring roughly seven metres along its longer axis and 6.6 metres across. The second, a little to the northeast and broadly similar in form, is somewhat larger, running approximately 9.5 metres by 5.8 metres. Both are read as probable indicators of a souterrain below, the word probable doing real work here, since the underground chambers themselves have not been excavated or formally confirmed. They belong to the wider context of the rath, a roughly circular raised enclosure of the kind that served as a defended farmstead in early medieval Ireland, typically dating from somewhere between the sixth and twelfth centuries.