This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

A tree-like building perches on its trunk in the Steglitz neighborhood of Berlin.

Berlin's old airport.

A surreal museum of extraordinary industrial objects.

An eerie, derelict amusement park in Berlin.

Established in 1638 to battle the Black Death, Hortus Botanicus Amsterdam is a treasure trove of rare flora.

The world's first zoo for microbes collecting the horrible and wonderful things living on and around us.

The world's only museum devoted to the wonders of fluorescence.

Catalonia Tradition: Beating the hollow Christmas log until it defecates in your fireplace.

The former 1920s mansion of a prominent Catalan developer was used as the Soviet Embassy during the Spanish Civil War, and there is still a bunker below the garden.

One of the most photographed buildings in a city known for its Modernista architecture is an abandoned squat.

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

The studio of Catalonia's most famous theatrical designer remains exactly as he left it.

A once-secret library of Freemason history in Catalonia.

18th century anatomical amphitheater of the Royal College of Surgery of Barcelona.

This Funeral Hearse Museum represents the finest in cadaver transportation.

A temple to modernity, tucked away amid Barcelona's more well known museums.

One of Europe's largest supercomputers is housed inside of a disused chapel.

Bask in the 19th century grandeur of an eccentric Freemason millionaire's private gardens.

Turntable anonymously received orphans, alms, and groceries.

Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

Week-long block party becomes a competition for the best decorated street.

An unusual stroll through gentlemen's erotica demonstrates that pornography is timeless.

Gaze upon chocolate sculptures depicting everything from chariot races to Gaudí's famous church at this shrine to sweets.