National Geographic Adventure named the diving at Bonne Terre Mine in Missouri one of the top 10 adventures in America, and it's easy to see why. Back in the day, the mine's deepest reaches were not underwater. A massive pump system stemmed the flow of encroaching groundwater as the miners pushed ever deeper. But when this, the world's largest lead mine, was all mined out, the pumps were turned off and the water trickled in to fill the void. These days, mine owners Doug and Catherine maintain a constant water level providing divers with access to their unique underwater vision.

The dive deck hovers on the water's surface, 150 feet from terra firma. Underwater pillars, shafts, archways, walls and ceilings stretch for miles in all directions, a sprawling maze beneath the town. Artifacts like shovels, drills, ladders, and ore carts lay everywhere. You'll also be struck by the electricblue water, the result of 500,000 watts of high-powered stadium lighting installed by the owners. There are more than 50 planned trails open to the public and the experience is accessible to most divers. Every group of divers is assigned a guide and a safety diver and the divers dive the trails in a preset sequence. The dives become more advanced with additional swimthroughs and archways to navigate as the numbers get larger. Under special circumstances, exploratory dives are possible here as well. Dubbed "Bear Trails", these more advanced, guided dives delve into the unlit and underexplored sections of the mine. Bear Trails are only for divers who prove they've got the skills and the air consumption to make these dives.

This is the lure of what the Bonne Terre crew has dubbed "deep earth diving," a seemingly endless underground world, frozen in time.

ACCOMMODATIONS: On-site, Diver's Lodge and Bunk House, or stay at the 1909 Depot Bed & Breakfast has four bedrooms and two detached train car suites. AMENITIES: Whistle Stop Saloon; gear rental. CONTACT INFORMATION Toll-free: 888-843-3483 Website: 2dive.com E-mail: [email protected]