Bonne Terre Mine, Missouri

A year-round open-water training site, in the heart of the Midwest, is how Doug Goergens likes to promote Bonne Terre Mine, an underground dive site 60 miles south of St. Louis. The former St. Joe Lead Mine contains the remnants of a mining operation that started in 1870 and lasted nearly a century. In 1961, miners walked away, leaving spring-fed water to engulf their tracks, tunnels and a virtual museum of mining equipment. The world's largest underground mine became the largest underground lake. In 1974, the mine joined the National Register of Historic Places. Except for walking tours, little else occurred at the mine until the arrival of Goergens and his wife, Cathy, owners of West End Diving in St. Louis. Looking for an alternate place to stage open-water training dives, the couple eventually bought the mine, and by 1981 had turned it into a dive destination. Mere words can't accurately describe the size of the underground treasure. There are 17 miles of navigable shoreline, 24 dive trails illuminated by 500,000 watts of lighting, and a dive platform. In September, the mine hosted the first underground wakeboard competition, which is scheduled for broadcast November 9 on cable TV station TNN. Each weekend groups of 10 people are guided by a lead diver and assisted by a safety diver who follows behind. To ensure optimal appreciation for the environment, dive lights are not permitted. Bonne Terre easily accommodates divers of all levels. A c-card is all that's required.

Depths to: 100 feet (30 m); the average depth being 40-60 feet (12-18 m)

Visibility: Exceeds 100 feet (30 m)

Water temperature: 58 degrees Fahrenheit (14 degrees Celsius) year-round. A 7 mm wet suit or a dry suit is recommended. There is no thermocline.

Marine life: None but history is the draw. "Indiana Jones" underwater, is how one staffer described it. Mammoth architecture, calcium falls, oar carts, scaffolding, grating, staircases, pillars, slurry pipes, a famed elevator shaft, among other things.

Fees: $65 per dive, two-dive minimum. Includes tanks, dive guide and safety diver. Rental equipment and dive packages are available.

On-site amenities: Tanks, training platform. The mine is in the middle of town where lodging and dining are available.

More info: Call West End Diving at (314) 209-7200 or visit www.2dive.com.

Open: 9 a.m. to 5 p.m. Saturdays and Sundays; earlier during the winter high season. Prepaid reservations are taken.

Getting there: From St. Louis, drive south on Interstate 55 to U.S. Highway 67. Take U.S. 67 south to Missouri Route 47.