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

One day a year it is legal to jump off of this astoundingly tall bridge that spans an Appalachian gorge.

Elvis's own personal tropical hideaway.

A Memphis park where you can walk the whole Mississippi River in one go.

Every day a troupe of pampered water fowl walk the red carpet to their favorite fountain.

This replica of the Greek structure is in the heart of Nashville.

What was meant to be a temporary exhibit is now a permanent fixture at the St. Louis Zoo filled with beautiful birds.

Speak to a companion on the other side of the room loud and clear through this architectural anomaly.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

400 million-year old limestone caverns nestled in the Ozarks served as shelter and a hideout for cultures throughout North American history.

This erect, phallic geological spire wasn't always named so domestically.

Eight rare Corvettes are swallowed up by a sinkhole in Kentucky's National Corvette Museum.

The world's longest known cave system.

The fifth-longest suspension bridge the world, connecting one Michigan peninsula to another.

This shallow cave got its name from copious amount of human bones found inside.

A sealed test tube said to hold Thomas Edison's dying breath was given to the inventor's friend and mentee, Henry Ford.

Island where motor vehicles are banned -- home to the only carless highway in the United States.

A slab of sandstone covered with mysterious 1,000-year-old rock carvings from a vanished North American culture.

There are eight natural springs around town, each with a slightly different taste.

Air Force Academy Chapel made of 100 identical tetrahedrons works to inspire those of all religions.

While most of the games in this arcade take quarters, that would have been a small fortune when they were made.

The highest bridge in America was built for an almost unnervingly small amount of money.

When ecosystems collide in the arid Southwest.

Strange red rock formations that have been attributed to a higher power for hundreds of years.