This one announces itself through pure absence. Within a ringfort at Oughtihery in County Cork, the ground holds the memory of a souterrain, an underground stone-lined passage or chamber typically used in early medieval Ireland for storage or as a place of refuge, that has left no visible surface trace whatsoever. There is nothing to see, which is itself the curious point.

The only record of the structure comes from P. J. Hartnett, who noted in 1939 that the site of a collapsed souterrain lay roughly twenty-five feet to the east, inside the bank of the enclosing ringfort. A ringfort, to use the plain description, is a circular area enclosed by one or more earthen banks and ditches, the most common type of rural settlement in early medieval Ireland. By the time Hartnett observed it, the souterrain had already failed inward, leaving only its location on record rather than any physical form. Decades of subsequent survey work have confirmed what he found, which is to say, nothing.