Bonne Terre, Missouri, United States

Bonne Terre Mine

Bonne Terre Mine in southeastern Missouri is the world's largest freshwater dive resort, operating since 1980 inside a former lead-and-zinc mine that was actively worked from 1864 until pumping stopped in 1962. With pumping shut off, groundwater filled the lower five of nine mining levels, creating a cathedral-like underground lake of more than a billion US gallons. National Geographic listed Bonne Terre among the top ten adventure destinations in the world. Diving is permit-only and run by West End Diving / Bonne Terre Mine; divers descend a former mine shaft and explore 24 marked underwater trails through chambers up to 27 metres deep. Original mining equipment is left in place: ore carts, locomotives, ladders, drilling rigs, the foreman's office, even an operational pump house preserved by the cold (14 C) clear water. Visibility is constant 30 metres or more under permanent floodlights. There is no native marine life to speak of; the attraction is the surreal, cathedral-scale geology and history.