At Killetragh in County Cork, there is a recorded souterrain, an underground stone-lined passage of the kind built during the early medieval period, typically as a place of storage or refuge connected to a ringfort settlement. The difficulty is that nobody has been able to find it for the best part of a century.

The ringfort itself, a circular enclosure of the type commonly built by farming families between roughly the sixth and twelfth centuries, still exists at Killetragh, though it is heavily overgrown and leaves no visible trace on the surface. Within or close to it, a souterrain was once reported. Writing in 1934, a researcher named Bowman noted simply that it was said a souterrain had been here, but could not then be found. That cautious phrasing, "it is said", suggests the knowledge was already at one remove even then, passed along by local tradition rather than direct observation. What Bowman recorded was essentially an absence, a place where something underground was believed to have existed but had either collapsed, been filled in, or never been precisely located to begin with. Decades of subsequent vegetation growth have done nothing to clarify matters.