Curious cave that stays a cool 56 degrees all year long.

The world's largest man-made underground caverns offer unparalleled underwater wonders.

Once an ambitious nature spa, these forest ruins now provide a serene monument to failure.

Erosion and time have created a naturally-formed water park.

European castle ruins in an American state park are actually the product of death and grief.

A late sculptor's last project was to turn this abandoned cement factory into a castle-themed amusement park.

Less a museum than a bizarre fantasy world created by artists and engineers.

Over 50 historic windmills whir away at this outdoor museum.

Only museum dedicated to women pilots, with personal artifacts from Amelia Earhart and other aviatrixes.

The future of roadside attractions is this sci-fi soda mecca that is home to a 66-foot tall neon pop bottle.

A whimsical tower with a spiral staircase, inspired by the Space Age and the Möbius strip.

An immersive art experience built by local arts collaborative, Factory Obscura, in the building formerly known as The Womb, a psychedelic arts center founded by the frontman of the Flaming Lips.

The world's only museum devoted solely to the art and collection of action figures.

An acoustic anomaly with a mysterious cause.

A one-of-a-kind sundial at the Very Large Array honors a radio astronomy pioneer, incorporating the original piers from his breakthrough radio telescope.

A sprawling collection of over 106,000 toys from around the world.

Wedding chapel's mysterious spiral staircase said to be miraculously constructed.

Despite time, colonization, and the brutal New Mexican heat, these Pueblo ruins still stand.

"I did this all while you were watching TV."

A multi-storied adobe complex has been inhabited for more than a thousand years.

These aggressively sustainable art homes look like something out of 1970's science fiction.

A phenomenal assembly of pueblos in New Mexico is the most complete example of ancient ruins north of the border.

Legends surround this jagged rock formation in the New Mexico desert.

A clear blue swimming hole with hidden caves, still unexplored.