A castle from the Holy Roman Empire that hosts traveling youth... in its stables.

An architectural oddity hides in plain sight on this iconic London bridge.

Portugal's National Pantheon has a history of curses, collapses and financial problems.

Alexander Hamilton’s creation caused quite a bit of controversy.

One of the indelible moments of the American Revolution took place at this location.

19th century cemetery hidden in Brooklyn's Prospect Park.

Little Red Lighthouse under the George Washington Bridge.

The blinking light atop the iconic landmark has been sending secret messages for decades.

Built hundreds of years ago this downtown iron barrier once protected a much despised king.

Two very green residential towers cleaning the air in one of Europe's most polluted cities.

The dramatic upward-curving roof is one of the most iconic examples of Googie architecture that still stands today.

American revolutionaries and British soldiers alike are buried here in the fourth-ever cemetery in Boston.

The most accurate timepiece in the world.

Once the future of underwater combat, this old sub is now open for visitors to muck around in.

This macabre masterpiece of a mural is one of Francisco Goya's "Black Paintings."

The notorious headquarters of a corrupt political machine.

This Rhode Island mansion was a stand-in for the exteriors of Collinwood in the original "Dark Shadows" series.

This high desert botanical garden is a unique display of Northern New Mexico's geology.

The final resting place of the great navigator, or maybe his brother.

It is said that each of the white stones in the red facade of this medieval house represents the head of a murdered Swedish noble.

Paranormal activity on the great lakes.

At one time this small mining village was the highest town in America but now it sits abandoned while the mine churns on.

The largest retailer of seashells in the world.

A once crucial portion of the Long Island railroad still lays abandoned, waiting to be turned into an urban park.