It is a narrow solution crevice, the kind formed when slightly acidic water works its way through soluble rock over long periods, widening natural joints into irregular passages. What makes this particular crack in the hillside worth attention is not its scale but its contents: bones of brown bear, elk, and Arctic lemming, deposited there somewhere between roughly 12,750 and 12,250 years ago, alongside, in later layers, the remains of at least two people whose presence has never been fully explained. When archaeologist Marion Dowd visited in 2003, she could not find the entrance at all, even though it had been mapped on Ordnance Survey editions of 1840 and 1897.

The cave's documented history begins in earnest with an 1904 letter from R. J. Ussher to R. F. Scharff, preserved unpublished in the National Museum of Ireland, in which Ussher describes three hours of digging in what he calls the 'superficial deposit of Red Cellar Lough Gur.' His tone is cheerfully unsystematic: he notes finger bones, pig remains, the metatarsals of small ruminants, and a scrap of leather, and mentions that the cave shows no sign of ending. The bones recovered from that investigation, later described in a handwritten report by A. W. Stelfox, include foot and ankle bones from an adult and a rib fragment from a juvenile; radiocarbon dating of the adult's talus returned a Neolithic date of around 4,671 years before present. A further excavation was carried out in autumn 1938 by the archaeologist S. P. Ó Ríordáin, whose results were never published. The bones he recovered, labelled simply as coming from 'a small fissure in the limestone known as the Red Cellar,' are now held in the National Museum under registration number NMINH:1938.169. His dig appears to have turned up further extinct animal remains but nothing that he considered archaeologically significant. The larger animal bones in the cave, including those of bear and elk, were most likely dragged in by scavengers such as hyenas or foxes rather than deposited by people.

The cave sits on the south-facing slope of Knockfennell Hill, roughly 30 metres south-east of the summit, where a ring-cairn, a type of circular funerary monument built of stones, occupies the high ground. From that slope there are open views north-east and east toward Knockadoon Hill, which carries an extensive spread of prehistoric settlement remains, and south-west toward Lough Gur Castle. The entrance, though marked on nineteenth-century maps, reads on recent aerial imagery as little more than rough, overgrown ground; Dowd's 2003 visit, during which she failed to locate it, is a useful reminder that visibility on the ground can differ considerably from what the maps suggest. Anyone looking for it should expect to search carefully along the hillside rather than walk directly to a clearly defined opening.