A favorite Paris bar for U.S. expats, including Gershwin, Hemingway, and James Bond.

A 300-yard long natural tunnel runs through a ridge deep in the Appalachian Mountains.

Behind the pink curtain, Au Bonheur du Jour, an art gallery of erotic archives.

The "Seinfeld" diner.

The largest drain hole in the world.

The world's highest and most dangerous infinity pool lies at the precipice of Victoria Falls.

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

Established in 1638 to battle the Black Death, Hortus Botanicus Amsterdam is a treasure trove of rare flora.

Iceland's "Smoky Valley" is a beautiful river that is shrouded in a constant cover of steam clouds.

This modern antique shop is a museum for 1980's Saturday morning cartoon culture.

A mysterious artist-run cabinet of curiosities and library.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

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

These eerie outliers of the lightning bug family glow a mysterious blue color.

The scuba diving training facility was named for the steam that rises from the cave's chimney.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

According to the local folklore, the myriad colors of this lake are the result of a lovelorn wizard's blunder.

A gargantuan crystal kingdom.

Stripes of flowers bloom each spring in a 50 acre rainbow of color.

This naturally-sourced hot spring is now home to a clothing-optional resort.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

Where manatees are the snowbird vacationers in these balmy Florida springs.

Giant busts of 42 U.S. presidents are sitting in a field in Virginia.

An Irish church where an 800-year-old mummy is reaching out of his coffin as if to shake hands.