In ancient times, these fallen standing stones supported a massive house.

Where hundreds of Japanese civilians committed suicide to avoid being captured by American soldiers during WWII.

A once-glowing grotto at the bottom of Waikapalae Wet Cave.

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

Once adorning a New York skyscraper, these reclaimed ruins now haunt an Indiana park.

A hidden network of subterranean passageways lies tangled beneath Indianapolis' bustling City Market.

Finnish lake, and scene of an infamous murder mystery.

According to the locals, the sands of this secluded Norway beach are infused with gemstone particles.

Tucked behind New Jersey's abandoned Gingerbread Castle lie the eerie ruins of a once-flourishing paper mill.

An open-air museum in a mountain valley features works designed to blend in with—and disintegrate back into—their natural surroundings.

An architect transformed this abandoned cement factory into his castle-like workshop.

Brisbane's manmade urban beach has enough water to fill five Olympic-sized swimming pools.

An exact replica of a colossal Olmec head sits atop a pyramid within a Madrid traffic circle.

This tangled English forest looks like something right out of a fairytale.

400-year-old garden, restored to beauty.

A fantastic castle rumored to be the birthplace of King Arthur.

A circle stone within a stone circle.

A lakeside garden in the Southern Alps full of whimsical artwork and thousands of beautiful flowers.

The ruins of an ancient island city built atop a coral reef in the South Pacific are spectacular and strange enough to have inspired H.P. Lovecraft.

Unlike many reclaimed, abandoned mines, this Canadian cave system is still just a dangerous maze.

An abandoned stretch of elevated road in the middle of the Brazilian jungle.

An apocalyptic seismic event creates a deadly chain reaction that ends with a 6-mile long lake developing within weeks.

This massive subterranean fissure is known as the "underground Grand Canyon."

A seemingly endless landscape of pure salt stretches far across Bolivia.