Stockholm's narrowest alley is barely over two feet wide.

Although rarely used, there is still a hidden room for the royal family at the Stockholm central station.

It's always game time at Stockholm's only museum devoted solely to video games.

It is said that each of the white stones in the red facade of this medieval house represents the head of a murdered Swedish noble.

Stockholm's deepest subway station is also a stunning ecological wonder.

Sweden's "good old days" painstakingly re-created in a model village.

It houses the remains of a 17th-century version of the Titanic.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

A random tree outside a Budapest hotel has become a DIY shrine to the late singer.

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

Once the home of a hermetic monk, this cave now houses a small church.

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

A series of playful yellow penguins share a serious message about the environment.

The slender brass strip in Prague's Old Town Square was used to tell time from 1652 to 1918.

A surreal statue honoring Prague's favorite literary son.

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

Macabre astrological automaton clock dating to the late 1400s.

Two stunning 17th-century libraries and a cabinet of curiosities.

The iconic boulevard is the perfect place to catch sight of a bicycling skeleton, a levitating Satan, or a chef with his head stuck in a pizza.

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

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

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

Once a black market electronics marketplace, now an otaku shopper's paradise.

Not quite the menace it once was, this monster still has some chops.