Finale of "William Tell Overture" can be heard as drivers pass over grooves in the road.

A winding path built in secret on the edge of the continent.

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

This structure among the trees was the result of divine inspiration.

Wondrous sandstone hoodoos where Native Americans collected clay for pottery, 9,000 years ago.

Notorious artist squat renovated into legal studios.

The world's northernmost ice hotel.

This historic train station has been converted to a locomotive themed hotel.

A sinuous path among steep cliffs creates a stunning sight in southwestern Serbia.

She asked for a potato cellar and over the next 23 years he gave her a network of holy caves.

Unparalleled stargazing, one of Colombia's best observatories, and a swimming pool can all be found in the middle of this ancient tropical forest.

What was once the largest NFL stadium.

The remains of an ancient settlement in one of the oldest archeological sites in South America.

This extravagant Art Nouveau rest stop features a million-dollar view of the Columbia River.

An old asylum graveyard that's been abandoned for half a century attracts those seeking a dark thrill.

This pristinely abandoned filling station on the edge of a graveyard is populated solely by unsettling mannequins.

This underground church is topped with a 500-foot cross that is seen by many as a beacon of fascist hubris.

A Lycian city of the dead carved into the hillside of Southern Turkey, complete with startlingly human touches.

This off-limits room in the National Library of France is home to a system of pneumatic tubes, once used to bring books to readers.

Where thousands of slaves passed through the "Door of No Return."

Lonely industrial sculptures in South Australia created by a mechanic turned artist.

This eccentric cave dwelling is bizarre even by the standards of a subterranean town.

A desert that rolls right up to the ocean, where it's so dry animals live off the fog.

High atop a Mexican rainforest mountain, this ancient pyramid once drew pilgrims countries away.