Introducing Wind Cave National Park
This park, protecting 44 sq miles of grassland and forest, sits just south of Custer State Park. The central feature is, of course, the cave, which contains 132 miles of mapped passages. The cave's foremost feature is its 'boxwork' calcite formations (95% of all that are known exist here), which look like honeycomb and date back 60 to 100 million years. The strong gusts, which are felt at the entrance, but not inside, give the cave its name. The visitor center has details on the variety of tours that are offered. The four-hour Wild Cave Tour offers an orgy of spelunking.
Hiking is a popular activity in the park, where you'll find the southern end of the 111-mile Centennial Trail to Sturgis. The campground rarely fills and backcountry camping (free with permit) is allowed in limited areas.