#6 Lake Cumberland, Kentucky

  Lake Cumberland, Kentucky

If you're a kid, or you want to be one again, try a family vacation below ground among the last truly unexplored land that's left. Caving, or spelunking as it's commonly known, requires only a curious mind and a lack of claustrophobia. Let your imagination run wild as you explore a whole new world!

One of the best places for caving is Kentucky's Mammoth Cave National Park. This 350-mile-long cave system - the largest in the world - has been home to Native Americans as early as 8,000 B.C; Jesse James and his gang in the 1800s (according to legend); and even a night club in the early 20th century. Today it's a carefully preserved wonderland of what rocks, water and time can do: "soda straws," vertical shafts, onyx and, of course, stalactites and stalagmites - wondrous forms of nature that you'll never see above ground. Much of this hasn't been seen for some 2,700 years.

Among the many tours provided by the U.S. Park Service is the Trog Tour, an off-trail adventure just for kids 8 - 12. It begins at the cave's Historic Entrance and features a first-hand look at this new world by foot, hands, knees and belly. And it really is a new world, with locations including the Rotunda, Giant's Coffin and Broadway Avenue.