This one offers nothing at all. On the southern side of a ringfort at Knockacarracoosh in north Cork, there is said to be a souterrain, an underground stone-lined passage or chamber typically associated with early medieval settlement, used variously for storage, refuge, or ventilation of adjoining structures. Whether it survives beneath the soil in any meaningful form is unknown. There is no visible surface trace.

The sole record comes from a 1934 reference by Bowman, who noted the site of a souterrain on the south side of the ringfort. That phrasing, "site of," already carried a note of uncertainty ninety years ago, suggesting even then that whatever had been there was no longer easy to identify. The ringfort itself, a type of enclosed farmstead common across early medieval Ireland, provides the broader context, but the souterrain remains the more elusive feature, known only by its mention and its absence.