The Aillwee Caves, near Ballyvaughan, County Clare, Ireland, were discovered by Jacko McGann, a herdsman on Aillwee hill who went on to explore the cave complex extensively by candlelight. The caves were opened to the public in 1976 after a group of cavers continued the exploration up to the point where a huge fall of boulders blocked the way (about 210 metres in). It has since been extended, and is one of Clare's major tourist attractions, as part of the Burren micro-environment.
Its features include limestone stalactites and stalagmites, an underground river and several caverns. There are also relics of brown bears who used to make their homes inside Aillwee hill. These bears have been extinct in Ireland for several thousand years, so the discovery of these signs was quite exciting for Irish archaeologists. The caves themselves were formed by the erosion of the inside of the hill by streams which sank through the limestone over hundreds of thousands of years, and was accelerated by the melting and freezing of several ice ages.
The tour of the Aillwee caves is really quite boring, as there is just a single narrow path and guard rail which leads through the caverns. The climactic moment comes when the tour guide calls for the lights to be switched out. The resulting total darkness would be interesting and wonderful if not for the inane chattering and gasping of one's fellow tourists.
The Official Aillwee Caves website: www.aillweecave.ie