These tombs were built into the side of a mountain so that ancient angels could reach the dead.

Tasked with beautifying a disused stretch of industrial land one artist filled a hole with grass.

For those going through a life transition, a place to leave behind a piece of your former self.

The enormous 250-room Vanderbilt mansion conceals hidden doors and secret passageways.

This series of Scottish caves has no clear purpose other than baffling historians.

Each of these gorgeous, intricately decorated rooms is painstakingly crafted to the scale of 1 inch: 1 foot.

Both the World War II Allied Forces and NATO have used this modern bunker underneath Malta’s capital.

The hidden lair of an alchemist rediscovered in a 2002 flood.

Along the most northwestern point in Africa is an ancient cave surrounded by legends.

These wondrously illuminated caverns extend under the mountains of the Fukushima Prefecture.

An immense cave that has served as an outlaw's treasure trove, an underground dance hall, a nuclear fallout shelter, and much more.

This partially buried wreck is one of the most complete of its kind but is only revealed when the sea allows.

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

Roots and stumps that lay inundated for two millennia are on display in Japan's city of three mysteries.

Like a kitschy mirage in the Mojave, this eatery serves up classic 50s-style diner meals and a dinosaur sculpture garden.

A retired schoolteacher in suburban Nevada transformed his front yard into a paleontological menagerie.

Unscathed for almost 2,000 years, the best preserved Roman triumphal arch is in a small southern Italian city.

This curious gravestone tells the legend of an unknown mariner's grisly murder.

A Manhattan office building is home to the world’s largest chess board.

A miniature rainforest is growing inside of a Midtown Manhattan office building.

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

Hidden in an ordinary Midtown building is a one-room museum dedicated to the greatest escape artist.

Hidden in plain sight on a pair of Manhattan subway tunnels are a pair of public instruments that sing to each other.

An unassuming secret door once led to a legendary watering hole.