A one-of-a-kind collection of a unique medium.

A massive underwater sinkhole made famous by Jacques Cousteau.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

A collision of human error and natural geothermal pressure created this rainbow-colored geologic wonder.

The neon signs from Las Vegas' past find their final resting place at this unusual graveyard.

A tiny museum housed in a New York freight elevator specializes in the "overlooked, dismissed, or ignored."

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.

An exquisite tunnel of cascading flowers.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

A huge musical instrument played by the ocean.

This astonishingly geometric cave has inspired everyone from Jules Verne to Pink Floyd.

There's a 12-foot-tall replica of the Washington Monument hidden under a manhole nearby.

The privately owned cemetery that holds room for Washington's finest when they step down from life.

A Civil War fort in the middle of Washington, D.C. has been swallowed by a forest.

Enormous piles of historically significant stones, dumped by Congress in a forest, and abandoned for 60 years.

A record-size collection of wild-haired troll dolls tells the story of the mythical creature's roots in Scandinavian folklore.

The colony of South Australia was proclaimed on a hot December day under a distinctively arched gum tree.

Literally a million fascinating cartographic artifacts are held in this sprawling university collection.

American involvement in World War I officially ended in 1921 in New Jersey, three years late and thousands of miles from the battlefield.

Two hundred tons of pioneer artifacts were painstakingly recovered from a shipwreck at the bottom of the Missouri River.

The remnants of an archaeological camp stand within Tikal National Park.

One of the world’s most colorful cemeteries, where each pigment is symbolic.

You can cross from one country to another in a single hop on this little bridge.

A whimsical, punny collection of "fence art" outside the tiny mountain town of Baker, Nevada.