Within a ringfort at Island-Dahill in County Cork, there is said to be a souterrain, one of those stone-lined underground passages or chambers that early medieval communities used for storage or refuge, but nobody has been able to locate it. The interior of the fort is overgrown, and there is no visible trace on the surface of anything beneath.

The trail of non-evidence goes back at least to 1934, when a writer named Bowman recorded the local tradition plainly: it is said a souterrain was in this fort, but same could not be found. That phrasing has a particular quality to it, the passive voice of accumulated rumour rather than direct observation. The ringfort itself, a roughly circular enclosure of the kind built across Ireland from the early medieval period onwards, survives as the physical context for the story, but whatever passage or chamber may lie beneath it remains unconfirmed, buried under vegetation and unverified by any excavation since.