America's post-nuclear-attack chambers of Congress.

A historic coal mine that doubles as a museum and tourist attraction.

A 300-yard long natural tunnel runs through a ridge deep in the Appalachian Mountains.

Mile-long cave system near Great Smoky Mountains.

Better known as the "Body Farm," this unique research facility has been studying how human bodies break down since the 1980s.

Enormous lake at the bottom of a unique cave system.

Bizarre Cavern.

Gorgeous cave resemble a winter wonderland.

A famed drink seasoned with an amputated toe, now on its tenth digit.

Home of an evil witch famous within southern folklore.

The world's longest known cave system.