This one is notable for what has not been found at all. Somewhere beneath the ground at Gowlane, in mid Cork, there may be a souterrain, an underground stone-lined passage or chamber typically built during the early medieval period and associated with nearby ringforts, often used for storage or refuge. The difficulty is that no one has been able to locate it with any certainty, and the ground itself offers no clues: there is no visible surface trace whatsoever.

The sole record of the structure rests on a single reference by Hartnett, writing in 1939, who noted a local tradition of a "cave" in the north-eastern quadrant of the adjacent ringfort. That ringfort is a real and recorded feature of the landscape, but the souterrain it supposedly contains remains entirely unconfirmed. Traditions of caves and underground passages attached to ringforts are not uncommon in Ireland, and they are not always wrong; souterrains can be well concealed, their entrances collapsed or deliberately blocked centuries ago. But tradition alone, without corroborating excavation or survey, leaves the Gowlane souterrain in an awkward category: neither confirmed nor dismissed, simply unresolved.