While not a resort in the luxury sense of the word, Bonne Terre Mine is a truly unique diving destination. A former lead mine and now the largest freshwater dive resort on the planet, this National Historic Site is known as the Billion Gallon Lake and features 24 dive trails. Jacques Cousteau explored this underwater marvel, where divers can discover calcium falls, the former elevator shaft and mining artifacts such as scaffolding and ore carts. The depth of average dives (led by guides and safety divers) ranges between 40 to 60 feet, and year-round 100-foot visibility is enhanced with more than half a million watts of underwater lighting. The ultracasual Diver's Lodge offers on-site accommodation; those who prefer more in the way of ambience can stay at the 1909 Depot Bed & Breakfast in town.