This deep cave was undiscovered for thousands of years until a local farmer followed a dog into it 50 years ago. Inside he found a huge cavern with 1,000m (3,280 ft.) of passages running straight into the heart of a mountain. He kept it to himself for decades before eventually spreading the word. Professional cave explorers later uncovered its magnificent bridged chasms, deep caverns, a frozen waterfall, and hollows created by hibernating brown bears. Brown bears have been extinct in Ireland for 10,000 years. Guided tours are excellent here -- generally led by geology students from area universities. There's a scary moment when they turn out the lights for a minute so you can experience the depth of the darkness inside. Tours last approximately 30 minutes, and are conducted continuously. On-site, there's also a craft shop, a farm shop, a cheese-making enterprise called Burren Gold Cheese, and the new Burren Bird of Prey Centre (tel. 065/707-7036; www.birdofpreycentre.com), a working aviary designed to mimic the natural habitat of the buzzards, falcons, eagles, and owls that live there. Visitors can observe the birds, learn about the center's breeding program, and watch flying demonstrations in an open-air arena at noon and 3pm daily (also at other times in summer).