This medieval castle overlooking the Elzbach river looks just like it did hundreds of years ago.

A slice of central Asia in the middle of Berlin.

Started as a kitchen garden, now the second largest botanical garden in the world.

The fairy tale castle of the "fairy-tale king."

One of Antoni Gaudí's least-visited works, an homage to Catalan patrimony that mixes neo-Gothic with Modernista forms.

Barcelona's only remaining tram system takes riders to the Tibidabo funicular.

An early 20th-century bullring converted into a modern shopping center.

Occupied for six centuries by Franciscan Order nuns, this monastery is an amazing ode to Catalán Gothic architecture.

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

An existential riddle in the world's largest ancient castle.

An Orwellian sculpture with eyeball cameras watches passersby.

An eerie, existential museum dedicated to the author of "The Metamorphosis."

A lush indoor jungle fills this bustling Madrid transportation hub.

One of the oldest, well-preserved water treatment facilities in all of Europe.

A massive, abstract lookout tower providing a panoramic view of Prague.

A mansion where wonders of Christmas are celebrated all year long.

The rusted creatures wait to be discovered in Prague's botanical garden.

600 stumps, branches, and trunks of different shapes and sizes.

A giant interactive periodic table with real samples of the elements.

A surreal statue honoring Prague's favorite literary son.

The history of occult science is turned into a creepshow at this lurid Prague tourist attraction.

A marine aquarium with an astounding variety of fish hides in the basement beneath the famous Palm House.

Since 1874, this macabre collection has developed into a museum devoted to Scotland Yard's mementos of dastardly deeds.

This hidden museum examines the complex history of the country's law enforcement.