Meant to resemble a massive tree, the building is the best example of Spanish organicist architecture in Madrid.

A lush indoor jungle fills this bustling Madrid transportation hub.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

Order cookies baked by cloistered nuns in a 400-year-old monastery.

Remarkably intact Roman stone fortifications have encircled this Spanish city for centuries.

An abandoned 6th-century monastery features a medieval map of the known world.

Museum houses an impressive display of the origin and artistry from the now-quaint invention's history.

A grotesque Fiji merman dwells within this traditional Dutch-style building.

World War II-era bunkers are hidden under the beaches of this picturesque park, which is still scattered with wartime watchtowers.

The United States' oldest Episcopal church still in active use.

This 1830s store is believed to be the site of Harriet Tubman's first stand.

The stone marker that Mason and Dixon placed at the eastern end of the famous north-south border they surveyed.

A tribute to two brothers' artistic endeavors.

Giant busts of 42 U.S. presidents sit, crumbling in a field in Virginia.

This tree is a living witness to the beginning of the Civil Rights Movement.

If it hadn't been caught in time, a flaw in the design of this Manhattan skyscraper could have led to its collapse.

An aptly-named street near the birthplace of the modern LGBT rights movement.

The longest continuous underwater road in North America was built at the insistence of Franklin Roosevelt.

A strip of modern stores in historic buildings.

The only gallery in New York dedicated to olfactory art and the exploration of scent in art.

A commemorative plaque hides a door that leads down to the New York Public Library's underground book bunker.

New York's southernmost subway station is whimsically wavy.

2,000 barrels of aging beer hidden in a warehouse at the Brooklyn Navy Yard.

Known as the "Forgotten City" it was home to industry, riots, artists, squatters, and to one of the largest single disaster fires in New York City.