Mammoth Cave, Kentucky
Credit: Danita Delimont / Getty Images

We like bourbon and horse racing as much anyone, but there's more to Kentucky than surface charms. The state is home to some of the world's biggest caves, including Mammoth, which extends 400 miles through the pocked limestone. "It's like Swiss cheese," says Vickie Carson, Mammoth National Park's public information officer. "You can see how water worked on the walls and carved out the passageways. There are some really beautiful places underground." The entrance chambers to the cave are indeed spectacular, with collections of stalactites and stalagmites that look like giant frozen waterfalls. The most singular view, however, lies deeper in the cave, where only guided expeditions are allowed to go. On the five-mile wild cave tour, spelunkers crawl, shimmy, and squeeze through holes barely bigger then a basketball to see places like Cathedral Dome, a pool-size room layered with limestone fluting that seems to morph as headlamp beams track over it. But the most memorable view requires that visitors turn off their lights. There are few places on Earth where mankind can still experience total darkness and complete silence. This is one of them.

More information: Cave tours cost $48 per person. Visitors can fly into nearby Bowling Green or Louisville, Kentucky, or into Nashville if they don't mind a bit of a drive.