steep natural entrance of Carlsbad Caverns. Rocky slopes and canyons, cactus, grass, thorny shrubs, and the occasional tree, who could guess at the hidden treasures deep underground? Beneath this rugged land are more than 117 known caves - all formed when sulfuric acid dissolved the surrounding limestone.
The Blue Ridge Parkway bills itself as "America's Favorite Drive"—it is, after all, one of the most visited spots in the National Park Service—and it's easy to see why. The road winds its way through 469 miles of Appalachian Highlands between North Carolina and Virginia before linking up with the Skyline Drive in Virginia's Shenandoah National Park.
This is a 54 mile route that travels through the Ouachita National Forest from Talihina, Oklahoma to Mena, Arkansas. The drive meanders along the top of the Ouachita, Winding Stair, and Rich Mountains, and provides spectacular views.
One of the nation's most scenic tunnels can be found in Utah. The Zion-Mount Carmel Tunnel on the highway between Zion National Park and Bryce Canyon National Park includes a series of "windows" in the sandstone walls, allowing drivers to look out over some pretty spectacular vistas. Don't forget to watch the road! Flickr/Bryan Ungard