An odd, ancient window that may have once been part of a brutal prison is embedded in the side of New York's Police Plaza.

The world’s oldest and biggest bookstore stocking only mystery, crime fiction, espionage, and thrillers.

Manhattan’s Battery Park has a whimsical carousel full of spinning, glowing fish.

This vertical pinnacle in China was the inspiration for the floating mountains in the movie “Avatar.”

The magical, mossy forest that inspired Princess Mononoke.

A terrific purveyor of natural history objects and curios.

The angel of death appears to weep black tears at this grave marker.

The longest continuous lava tube in the continental U.S. offers 2.5 miles of dark explorations for the adventurous.

This natural wonder drops 16 stories straight down through rare flora and streaming waterfalls.

A modernist landscape of water and sci-fi concrete.

A stunning, two-tiered waterfall made famous by poets, artists and the legend of a ghost dog.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

A self-built castle made by a mysterious man.

This abandoned asylum was once a state of the art facility before devolving into one of the most deadly mental institutions in American history.

Odd outsider art installations surround a Gold Rush-era ghost town.

A hands-on traveling collection of the innovative devices of yesteryear.

The world's only international cryptozoology museum is host to an unrivaled collection of mysterious objects.

An underwater city for the dead.

A breathtaking array of ancient Pueblo structures and artifacts counterintuitively preserved by neglect.

A Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

Rainbow-hued local gem in Venice.

Hidden in Central Park's Ramble is a troublesome cave buried just beneath the surface.

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

Just a few miles from downtown Atlanta is a trail covered in a crazy collection of outsider art.