Coastal dunes, site of buried Egyptian movie set and former utopian colony.

Planned as the world’s first zero-carbon city, it had lofty ideals—but is only 5 percent completed and aiming for 50 percent carbon-neutral.

This open air cathedral invites all faiths to worship under the only roof big enough to fit them all: the sky.

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

Decades after testing the polio vaccine on unwitting patients, this historic mental hospital sits in ruin.

An abandoned asylum where patients have been forgotten but their possessions remain.

An elevator into the Baltic Sea.

A spiral staircase twists to the top of this unusual Czech lookout tower.

The legendary court where emerging basketball players gain their street cred.

A warning to the weak-kneed: This narrow bridge does its swinging eight stories high.

Ancestral Puebloan ruins, natural arches, and box canyons abound in this seldom-visited corner of Monument Valley Navajo Tribal Park.

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

This hidden stream beneath Indianapolis makes an appearance in the best-selling novel "Underground Airlines."

The latest in a series of long glass bridges suspended at terrifying heights.

As lake waters recede, a German village reemerges after more than a hundred years.

This Queens hospital has stood abandoned for almost 20 years after its patients were secretly relocated in the dead of night.

These powerful, if squat, Canadian waterfalls flow in different directions depending on the time of day.

Art Deco and “Wrenaissance” mash-up, this recently restored royal residence has been home to kings and comes with secret monkey passages included.

At nearly 1,000 feet long, this astonishing glass suspension bridge is one of the longest in the world.

The first and only carousel with a lineup entirely of insects.

A subterranean playground in an abandoned slate mine.

A miniature Italianate fantasy village on the coast of Wales and the set of ITC classic "The Prisoner."

A solitary tree has grown up all alone on Lake Wānaka, backdropped by the beautiful Southern Alps.

An abandoned tank sits in an empty London lot as a symbolic middle finger to local city planners.