A disquieting Aztec sculpture displays hundreds of stone skulls representing the victims of human sacrifice.

The abandoned ruins of a beautiful medieval castle just outside Barcelona.

These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.

This cemetery features modernist statues as strange as its name.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

The only surviving piece of Copenhagen's 16th-century defensive wall.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

Danish tourist destination well known for open stalls where vendors sell marijuana on the street.

Hans Christian Andersen for the postmodern world.

The de facto symbol of Copenhagen is this bronze fairytale which cannot seem to keep its head for very long.

A small museum in the Bay of Pigs gives the Cuban perspective on the famously failed U.S. invasion.

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

His music once banned in Communist Cuba, John Lennon is now immortalized in bronze by Castro, who considers Lennon a "fellow dreamer."

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

A Cuban artist reclaimed his impoverished neighborhood as a dreamy folk art kingdom.

Every Sunday, Bogotá turns 75 miles of its city streets into a bicycle superhighway.

The world's first crowdfunded skyscraper has not gone quite to plan.

Known as the site of 'El Dorado,' this mysterious lake is rumored to hold gold beneath its waters.

Cathedral carved out of salt, located a mile below the earth's surface.

Colorful lights and mirror-like brine pools create trippy illusions within the historic mine.

The little bear in the "funny kind of hat" has made his way from London back to Peru.

The mysterious "Candelabra of the Andes" could represent anything from a god's trident to a hallucinogenic plant.

This stone complex marks the urban center of a lost civilization.

A market for witches is hidden within a train station.