Oweynagat

Oweynagat — Uaimh na gCat in Irish, 'the Cave of the Cats' — is a narrow, low-roofed souterrain attached to a natural limestone fissure within the Rathcroghan complex near Tulsk in County Roscommon. To the writers of the 12th-century Book of Leinster it was dorus ifrinn na hÉireann, Ireland's doorway to hell: the most literal threshold in Irish mythology between the visible world and the Otherworld lying beneath it. On a dark hillside above the Connacht plain, with its carved Ogham inscription visible above the lintel stones, the cave was regarded as both the physical and spiritual entrance to the supernatural landscape of Cruachán — the complex of some sixty monuments that served as the royal and ceremonial centre of ancient Connacht.

The cave's mythology is concentrated in Samhain, the festival at the dark turning of the year. Medieval texts in the Dindshenchas and the Adventures of Nera (Echtrae Nerai) record what emerged from Oweynagat on Samhain each year: a three-headed monster that devastated the land; saffron-coloured birds whose breath withered crops and blighted cattle; and a herd of supernatural pigs that multiplied whenever counted and stripped every field they crossed. In Bricriu's Feast, Cúchulainn faces wildcats pouring from the cave entrance before he subdues them — a tradition that may explain the cave's 'Cat' name. The Adventure of Nera centres entirely on Oweynagat: the warrior Nera follows a phantasmal procession into the cave and discovers a whole Otherworld city inside it, with a parallel Connacht existing beyond human time, through which the Cattle Raid of Cooley is foretold.

Oweynagat is also described as the dwelling of the Morrígan — the great triple war goddess whose role as battle crow, fate-weaver, and sovereignty goddess makes her the most powerful supernatural figure in the Ulster cycle. The cave's lintel stones preserve two early Ogham inscriptions from the early Christian centuries, suggesting the site was already marked and significant before the medieval texts formalised its mythology. The wider Rathcroghan complex — though largely unexcavated — is considered one of the most archaeologically and mythologically significant unprotected monument groups in Europe, and Oweynagat remains its most charged and specific focal point.