This one is remarkable for what it almost certainly no longer does. Within a ringfort at Duarrigle in north County Cork, there was once said to be a souterrain, an underground stone-lined passage or chamber built during the early medieval period, typically used for storage or as a place of refuge. At some point, it vanished. Not metaphorically, not administratively, but physically, leaving no surface trace whatsoever.

The only account of it comes from Bowman, writing in 1934, who recorded the tradition plainly: a souterrain was said to have been here, but there was no sign of it even then. That phrasing, "was said to have been", is itself telling. By the time Bowman noted it, the feature had already slipped from observable fact into local memory, the kind of thing older residents recalled but the ground itself no longer confirmed. Whether it had collapsed inward, been deliberately filled, or simply eroded beyond recognition is unknown. The ringfort it belonged to survives as a separate recorded monument, but the souterrain exists now only as a footnote to a footnote, a structure catalogued precisely because it cannot be found.