Mother Nature outdoes herself with this stunningly beautiful set of caves carved into marble.

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

The world's largest bioluminescent area was undiscovered by science until 2005.

Elaborate patterns adorn the city's disappearing traditional architecture.

The most alien-looking place on Earth.

A city built from mud and known as the "Manhattan of the desert."

One of the most remote and isolated villages on the Arabian Peninsula.

Yemen's "Stone Palace" looks like it was carved right out of the tall stone column on which it is built.

A massive forgotten storehouse from 1913 on the Brooklyn Waterfront has a spectacular view of Brooklyn.

A futuristic climate change study is nestled deep within this public land.

Behind a bodega is a small museum of relics and ephemera showcasing the history of New York.

This leafy estate is worth $18 million and is so grand it has two mailing addresses.

Blighted Irish field and the ruins of a 19th-century cottage on the edge of urban Manhattan.

A regular looking rock with an unbelievable history.

Taste the white whiskey that the United States' first president once distilled and enjoyed.

The Pentagon sits on a former island that was in Virginia at low tide and D.C. at high tide.

Conveniently located within binocular range of a nuclear bunker, the "summer camp" area was a painfully obvious spy house.

Please don’t anchor your boat onto the Department of Defense’s underwater data cables.

A former major munitions plant that has been converted into a sprawling art space.

The remains of a historic plantation nestled in between a parking lot and the rental car return at Reagan National Airport.

The tomb was guarded by soldiers from both sides of the war, and some left their initials carved in the brick.

Scenic mount trashmore, Virginia Beach's most curious waterfront still has a couple of secrets.

The first American woman to win the Nobel Prize in literature came from the foothills of Appalachia.

Bubbling up from deep underground is the warm crystal clear water that fills the Warm Springs Pools, America's oldest spa.