(Photo: National Park Service)
Mammoth Cave National Park, Kentucky
This park's famed cave system—more than 400 square miles of explored underground caverns that make up the world's longest—is the reason most visitors make the trip. But don't overlook the scenery aboveground. Forests of oaks, hickories, gum trees, and dogwoods on rolling Kentucky hills become a mosaic of fall colors this time of year.
When to Go: Check KentuckyTourism.com for updates.