Irish: Uaimh na gCat
The entrance to Oweynagat
The cave has become the focus of many wild legends: it is mentioned in the ancient epics of the island, in particular the Táin Bó Cúailnge ('The Cattle Raid of Cooley') and even into the early modern period local folk insisted that Oweynagat was an entrance to the Otherworld of pre-Chritsian Irish legend, as was described in the mediæval period as "Ireland's Gate to Hell". The cave has associations with the pagan festival of Samhain, Halloween, as well as being described as the "fit abode" of Morrigan, a goddess of pre-Christian Ireland.
The Irish name for this site is Uaimh na gCat which translates as 'Cave of the Cats'.
The cave is a natural (and not supernatural), narrow limestone cave with a man-made souterrain at the entrance.
At the end of the first century, a number of raths were built on the site. Some of these later included souterrains with an entrance for one built over Oweynagat using standing Ogham stones from the site that were unique to Connacht, usually only appearing in the south-west of Ireland.
Originally the entrance to the souterrain was contained within an earthen mound, but this was disturbed by the construction of a road in the 1930s. The souterrain is constructed of drystone walling, orthostats and lintels, and measures a total of approximately 34 feet from the entrance to the natural cave. The natural cave extends for a further 121 feet.
It is unclear whether what is referred to as the síd is Oweynagat or the mound of Rathcroghan itself. However, it is from Oweynagat that various destructive creatures emerged. The Ellen Trechen was a triple headed monster that went on a rampage across the country before being killed by Amergin, the father of Conall Cernach. Small red birds came from the cave withering every plant they breathed on before being hunted by the Red Branch, also herds of pigs with similar decaying powers emerged from the cave with Ailill and Medb themselves desperately trying to hunt them but having to deal with vanishing powers and an ability to shed captured flesh. The name Oweynagat may come from the magical wildcats featured in "Bricriu's Feast" that emerge from the cave to attack the three Ulster warriors before being tamed by Cúchulainn. The name could also refer to the king of the cats, Irusan, who features in Irish fairy tales and was believed to live in a cave near Clonmacnoise but is associated with many places. A tale from the eighteenth century tells of a woman who on trying to catch a runaway cow, follows it into the cave and emerges miles away in Keshcorran, County Sligo.
There is an ogham inscription on the overhead lintel just inside the entrance to the souterrain which reads ‘VRAICCI...MAQI MEDVVI’, which translation this would read ‘of Fraech, son of Medb’. Fraech is associated with Cruachan and Medb in the Táin Bó Cúailnge. Fraech is also associated with the nearby monument of Carnfee (Carn Fraích). There is a second ogham inscription on another lintel inside the passageway, barely visible, which reads ‘QR G SMU’. This inscription is too incomplete to enable a confident reading.
A historical reference to the cave is to be found in the Triads of Ireland, dating from the 14th to the 19th century, where Úam Chnogba, Úam Slángæ and Dearc Fearna are listed under the heading, "the three darkest places in Ireland". The last, meaning the 'Cave of the Alders', is generally thought to be the present Dunmore Cave, while the first two translate as the caves of Knowth and the caves of Slaney. It is not known which exact system of caves/passage tombs near the river Slaney is being referred to, with the most likely, those at Baltinglass. Other sources translate the listed locations as Rath Croghan, the cave or crypt of Slane and the "Cave of the Ferns".
- Molly Gowen and Lavinia Hamer "Birthsigns, The Celtic Animal Year" 1993
- Meyer, Kuno; Lavelle, Hilary; Purcell, Emer et al., eds (2005). The Triads of Ireland. Todd Lecture Series. 13 (1st ed.). Dublin: Hodges, Figgis & Co. http://www.ucc.ie/celt/published/G103006/. Retrieved 2010-11-06.
- J. C. Coleman (1965). The Caves of Ireland. Tralee, Co. Kerry: Anvil Press. pp. 14–16.
- Meyer, Kuno, ed (1906). The Triads of Ireland. Todd Lecture Series. 13 (1st ed.). Dublin: Hodges, Figgis & Co. pp. 4–5. https://archive.org/details/triadsofireland00meyeuoft. Retrieved 2010-11-06.
- Foot, Arthur Wynne (1878). "An account of a visit to the cave of Dunmore, Co. Kilkenny, with some remarks on human remains found therein". Journal of the Royal Society of Antiquaries of Ireland. 4 (Dublin) I: 65–94. https://archive.org/stream/journalofroyalso11royauoft#page/65. Retrieved 2010-11-06.
- Waddell, John (1998). The prehistoric archaeology of Ireland. Galway: Galway University Press. ISBN 1-869857-39-9.
- Smyth, Daragh: 'A Guide to Irish Mythology' (1988)
- Herity,Michael: 'Rathcroghan and Carnfree' (1991)
- Keating, Geoffrey: Foras Feasa Eirann", 1636
- MacFhirbhisigh, Dubhaltach: Leabhar Mor nGenealach" (1649–1666)
- O Flaithbheartaigh, Ruaidhri: Ogyia" (1684)
- Waddell, John:
- 'Rathcroghan: A Royal Site in Connacht' (1983)
- 'Rathcroghan, Co. Roscommon: where the Táin Bó Cúailnge began' (Archaeology Ireland Heritage Guide No. 44 (2009)
- Mallory, J.P. 'A provisional checklist of Crúachan in the Annals': Emania': Bulletin of the Navan Research Group No.5 (1988)