At Cloonagleavragh in County Sligo, official records have long noted the presence of a souterrain, an underground stone-lined passage or chamber typically built during the early medieval period, often used for storage or refuge, set within the earthworks of a rath, the circular enclosure that once marked a farmstead of some status. It is a combination that appears with reasonable frequency across the Irish landscape. The difficulty, in this case, is that nobody has ever been able to locate it.

When the site was assessed in 1995 for inclusion in the Record of Monuments and Places, the souterrain was formally catalogued as a feature of the rath at this location. Yet on the ground, no physical trace of it has come to light. More striking still, there is no local tradition of a souterrain here at all. That second absence matters as much as the first. Souterrains, even when long collapsed or deliberately backfilled, have a way of persisting in local memory, in field names, in cautionary stories about subsidence, or in the recollections of older residents who remember a hollow in the earth. At Cloonagleavragh, even that thread is missing. Whether the original listing was based on a misreading of an earlier source, a confusion with a nearby monument, or simply an error that travelled forward through successive records, is not currently known.