The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

Back in the tiny USSR.

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

World's largest bell sits on the grounds of the Kremlin in Moscow.

Moscow's imposing monument to the Space Age.

Former headquarters of the KGB.

This building holds the embalmed remains of the leader of the Bolshevik Revolution.

Immortal combat in a Moscow museum.

A former steam-powered mill from the 1800s is now an industrial park with a giant steel dragon slide.

Mountain where Jesus was first tempted by the Devil.

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

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

This semi-secret storybook hedge maze is also the oldest garden in the city.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

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

A little sculpture with a large wardrobe.

From Tintin to the Smurfs, Europe's greatest graphic icons are celebrated in a grand Art Noveau gallery.

Climb inside an iron crystal magnified 165 billion times its normal size.

Theme park featuring miniature replicas of European monuments.