The first full-scale tunnel built in America is short but scenic.

Live long and prosper in Tennessee.

Home to drunken tower-climbing goats... seriously.

Labor provided by Great Depression-era programs restored these 25,000 acres in Tennessee.

Walk the whole Mississippi River!

Mile-long cave system near Great Smoky Mountains.

Railroad came. People came. Railroad left. Town died.

More than five miles of underground passageways.

Visit this playground of waterfalls, caves and sinkholes.

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

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

Wild lights and sound effects turn a walk through some caves into an eye-popping 1960s tourist attraction.

All that's left of the quintessential "cabin in the woods."

The secret city built by the Manhattan Project.

Home of an evil witch famous within southern folklore.

Enormous lake at the bottom of a unique cave system.

For two weeks every June, fireflies in the Smoky Mountains perform an astonishing light show.