Aillwee Cave is a unique tunnel over 1 km long. The waterfall, surrounded by stalactites and stalagmites, is strikingly flood-lit from below. The bones of a brown bear were discovered in one of the hibernation caves, near the entrance. The sound of an underground river can be heard down a shaft in the largest chamber, even in dry weather. In the visitor centre, there is an exhibition explaining how the cave was formed.