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.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

An iconic Soviet statue of working-class people.

Gargantuan home of Russian science.

This massive monument honors the first human in space.

Moscow's imposing monument to the Space Age.

Former headquarters of the KGB.

Museum celebrating the achievements of the Soviet space program.

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

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

A whimsical bridge adorned with decorative dragons.

A public work of art that also provides some relief from the summer heat.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

A miniature train-ride through Slovenia's largest cave system.

This massive subterranean fissure is known as the "underground Grand Canyon."

A huge wooden clock that is so beautiful its creator was forcibly blinded.

These rare statues are one of the few remaining material witnesses to Old Prussian culture.

The site of the first battle of World War II.

These enormous, stern-faced statues greet visitors with lanterns, and sometimes costumes.

A monument to the defenders of the Arctic in Murmansk, Russia.