England's most famous front door has an accidental doppelganger.

The pretty iron lamp is a reminder of the architecture underneath London's streets.

This 700-year-old storehouse was a POW jail, aviation workshop, and Titanic memorial before becoming a brewpub.

The rusting relics of Southampton's former luxurious flying boat industry.

Now a memorial to merchant sailors and Titanic victims, this medieval church was destroyed by bombing raids in 1940.

A half-mile-long stretch of medieval forts built after a devastating pirate attack persists amid the modern port city.

Strange masks and obscure costumes are housed in this old Madrid corrala.

Over two centuries old and counting, Madrid's massive botanical garden contains one of Europe's only desert environments.

A Victorian Gothic masterpiece housing a world-class collection of rare books and manuscripts.

Also known as "Leicester's Folly," this almost cathedral was left unfinished and in ruins.

This tower is all that remains of a once-famed chapel.

Picturesque ruins once held off mighty armies.

The mysterious large white cross visible from the runway is a memorial to a massacre during Spanish Civil War.

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

Built to power trains, the engines in this building provided the entire city of Madrid with electricity during the Spanish Civil War.

Replicas of fossils unearthed during renovation work reveal how this area would have looked millions of years ago.

These abandoned country fairgrounds are filled with replicas of Spanish monuments.

This technological marvel is one of the world's first 3D-printed bridges.

This small museum tucked within a subway station holds pieces from Madrid's past.

An old, deep well, connected with a miraculous, divine rescue and the patron saint of Madrid.

This postmodern apartment block was designed to be a vertical neighborhood.

Part of the medieval watchtower is displayed in an otherwise ordinary parking garage.

An ancient Egyptian temple in the middle of Madrid, Spain.

A whimsical brother of the nearby Fallen Angel statue takes the falling part quite literally.