Spanish architects used seized Muslim gravestones to rebuild parts of the fortress.

A curious carving hides on a marble column in the Mosque-Cathedral of Córdoba.

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

The largest and best-preserved rotunda in Prague.

A quasi-futuristic roof sits atop a medieval Bohemian monastery damaged during World War II.

Looming communist pillar with a Czech twist.

Synagogue built from the stones of Solomon's temple contains the golem of Prague.

A mocking tribute to the past and modern leadership of Prague.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

Walk through Czech history in Prague's largest graveyard.

Macabre astrological automaton clock dating to the late 1400s.

The spot in the Mile-High City that's exactly 5,280 feet above sea level (at least for now).

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

Thanks to a quirk of elevation this gift shop produces magic doughnuts that are found nowhere else on Earth.

This former mining railroad is one of the best-preserved short lines in North America.

These huge stone ovens in the desert fueled the Nevada silver boom, and may have also been a hideout for outlaws.

Potential high level nuclear waste storage site for the next 10,000 years and beyond.

Dyed by iron oxide over centuries, these sandstone rocks rise thousands of feet into the sky.

A cemetery full of exquisite statuary, including a monument to a woman some say died of a broken heart.

After the Cuban Revolution, the famous rum company had to leave their swanky headquarters behind.

Once a favorite playground for the world's most illustrious guests, Hotel Nacional's secret weapons and bunkers reveal a more menacing side to its golden history.

A focal point of the Cuban government, this city square features one of the most iconic images in the country.

In terms of history and architecture, this is one of the most remarkable cemeteries in the world.