Dug as a secret royal escape route, the tunnel became a wartime bomb shelter and dumping ground for vintage cars.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

A World War II evacuation tunnel turned into a history display of Croatian state and people.

This modern, multimedia museum takes visitors on an evolutionary journey back in time.

Trimmed trees grow alongside the graves like topiary tombstones.

This 135-year-old weather station studied the effects of the climate on human health.

An ancient knight and a symbol of the city's freedom.

A tribute to an iconic act of defiance from the Croatian War of Independence involving a small car.

One of the best-preserved Roman amphitheaters is still used today, but for less brutal events.

This Croatian fairytale castle is slowly falling apart thanks to years of neglect.

Gargoyle head that brings good luck.

This truly palatial work of Communist-era architecture now sits crumbling on a Croatian beach.

Large, airy hallways hide within an impenetrable fortress that beckons urban explorers.

Where the lovelorn find a home for their sentimental keepsakes.

A musical instrument played by the sea.

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

Vienna's diversity-themed traffic lights were inspired by the Eurovision Song Contest.

This series of Baroque passageways in Vienna's cultural center mix old architecture with modern art.

Macabre museum devoted to historical Viennese murders.

This imposing memorial contains the remains of Che Guevara — and 29 other guerrillas who died with him in Bolivia.

Neo-cave art on the macro scale.

No one knows the meaning behind this giant sculpture of a nude woman with a fork riding a rooster in Havana.

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.