Four-story concrete hotel never opened to customers.

A trading post in the North Pole where children send letters.

This frozen tunnel in central Alaska is both an engineering feat and a valuable climate classroom.

Gorgeous cave resemble a winter wonderland.

Upside-down trees serve as natural flower pots in this hanging garden of Alaska.

The king of U.S. high points towers over every other peak on the continent.

Mind-blowing carvings and fantasy ice scenes grace the largest year-round ice environment in the world.

This whimsical stacked cabin looks like something out of a children's book.

Breathtakingly blue walls shimmer inside the "Glacier Behind the Town."

A cave's rare beauty held a cavernous secret hidden underground.

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.

In California, colorful roadside signs remind us all that love transcends borders.

These half-buried combine harvesters just off Route 66 are an homage to the Cadillac Ranch.

A pair of giant legs paying homage to a poem, a king, and it would seem, socks.

A sculpture made of 10 Cadillacs as a monument to the "Golden Age" of the American automobile.

A house turned museum is the real-life "home" of the fictional main character of The Wizard of Oz.

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

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

Dinosaurs invade a suburban Nashville neighborhood.

The hotel where Martin Luther King Jr. was shot is now a museum dedicated to his work.

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

Walk the whole Mississippi River!

This head-spinningly bizarre Depression-era art cave is wall-to-wall quartz and Jesus.