This natural marble cave is one of only five national monuments in Oregon.

A daring D-Day assault by U.S. Army Rangers is commemorated atop the high cliffs of this strategic point.

A life-sized mammoth sculpture marks the spot where the remains of a Columbian mammoth were discovered in 2005.

Where the polar bear watches over everything, and every drink is a double.

An off-grid art installation that encourages its visitors to imagine a world without waste.

Since World War II people have been decorating this stretch of the Yuma desert with signatures arranged out of rocks.

A fake town founded by Western movie stars is now becoming a hip desert community.

A music-filled, booze-soaked oasis in the desert.

A UFO-shaped event building originally intended to be a science museum showcasing the future.

Descend into the tunnels to experience the life of a coal miner.

Crouch down, stretch tall, and be sure to flail your legs to pay homage to the Monty Python classic.

This centuries-old gothic monster has been converted into a sprawling, glossy bookstore.

Walk through the actual strap iron cells and solitary chambers of Arizona Territory’s first prison.

Erroneously called the world's tallest flagpole, this landmark is devoted to "good neighborliness."

This giant shopping mall still holds signs of its automotive past.

A monument to a one-legged kidnapper, horse thief, and charlatan asks visitors to throw rocks in a pile.

Oldest existing church in New York and the inspiration for Washington Irving's "The Legend of Sleepy Hollow."

A very classy 1920s-era bar right in Grand Central Station.

The 28-foot granite map plots the locations of 40 theaters in New York City.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

The 20-mile causeway that separates the Netherlands from the sea.

A collection of 20th-century automata, penny arcade games, and musical contraptions.

Only hotel where you can legally launder money.

Plymouth's huge yet little-known memorial to the Pilgrims.