Wind Cave National Park

Drive to the mixed-grass prairie of southwestern South Dakota for cave exploration. This underground complex is one of the longest caves in the world with 149 miles of explored passageways. Reserve your place on a guided tour for your chance to see some rare rock formations.

Gaze at the walls and ceiling of Wind Cave to see honeycomb-like boxwork formations. They also look like square or rectangular boxes jutting out from the cave wall. Around 95 percent of all of the world's boxwork formations are in Wind Cave. This cave is the densest in the world, with the greatest amount of passages per cubic mile.

Discover the vast prairie above the cave, too. The park harbors the last remaining mixed-grass prairie in the United States. Watch for elk, bison, pronghorn sheep, and prairie dogs. You might see miles upon miles of wavy grass on wind-swept days.

Camp in the southern Black Hills at Elk Mountain Campground. There are 25 pull-through sites with no hookups or water.