There is nothing on the surface to indicate it is there. No depression, no lintel stone, no tell-tale hollow; the ground simply gives nothing away.

A souterrain is an underground passage or chamber, typically constructed during the early medieval period in Ireland, often built from dry-stone walling and covered with large capstones. They are found associated with ringforts, the circular enclosed farmsteads that once dotted the Irish countryside in their thousands, and are thought to have served as places of refuge, cold storage, or both. The ringfort at Johnstown is itself described as much defaced, meaning the earthen banks or walls that once defined its enclosure have been significantly eroded or disturbed over time. Within what remains of its northern half, the souterrain has caved in, leaving no trace visible from above ground. It is a site defined almost entirely by absence, by what has been lost or swallowed back into the earth rather than by anything a visitor could observe or touch.