Crag Cave is an ancient fossil cave system, older than mankind itself, within which can be seen the natural forces that created the complex and beautiful passages. The cave was once filled with water, which eroded the limestone rock into a maze of carved tunnels and chambers. In time the water dried up or found new routes, leaving deposits of river gravel and sediment. Small drips of water into the cave left behind crystals which formed the many features in Crag Cave, the most obvious of which are stalactites and
stalagmites. These delicate formations are an outstanding feature of the cave and, with its other features, make it the most exciting showcave in Ireland.