Crag Cave, Show cave in Castleisland, County Kerry, Ireland

Crag Cave is a limestone cave system outside Castleisland, County Kerry, with 3.8 km of surveyed passage on two levels. About 350 metres are developed as a show cave, reached by a man-made shaft and fitted with pathways, railings and lights. Calcite stalactites of various sizes grow from the ceilings, and the finest are lit by spotlights.

The Geological Survey of Ireland noted water-worn caves here in 1859, but exploration only began in 1981, when the upper passage was followed to a sump called the Green Lake. Hydrological tests showed the sump water differed chemically from the active streamway, suggesting dry passages beyond. Martyn Farr dived the sump in 1983, opening the large chambers; 1.6 km were then surveyed, and by 1985 the system measured 3.81 km. Local residents Donal and Margaret Geaney developed about 350 m as a show cave between 1987 and 1989.

The cave's Irish name is Pluais na Craige. It was found in 1981 while tracing streams that were polluting Castleisland's drinking water. Local residents Dr. Donal and Mrs Margaret Geaney, on whose land it lay, developed about 350 metres as a show cave between 1987 and 1989, adding a shaft entrance, paths, railings, lights and a music system.

The show cave section runs about 350 metres, entered through a man-made shaft built between 1987 and 1989, with pathways, railings and lights installed along the route. The full system extends 3.8 km on two levels, but only this developed stretch is open to visitors. The cave lies just outside Castleisland, starting at Glounsharoon and passing beneath the town to the Killarney Road.

The cave's only man-made entrance is a shaft sunk through the land of Dr. Donal and Margaret Geaney, who developed the show cave between 1987 and 1989. Before that, the first way into the large chambers beyond the Green Lake sump was Martyn Farr's 1983 dive.