A striking 12th-century-style castle built on the edge of a cliff.

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

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

The birthplace of an eccentric alchemist and possible inspiration for the fictional reanimator of monsters.

Putting the "mod" in "modular" since 2000.

A decommissioned tube carriage within a London museum hosts a regular pop-up supper club.

The secret wartime bunker built on the platforms of an abandoned Tube station.

Pop culture has helped to keep this iconic British building from being destroyed.

A little slice of Japan and its aesthetics in London's Holland Park.

The remains of Crystal Palace Great Exhibition of 1851.

A makeshift shrine to the late rock star is still kept up on the nondescript façade outside 1 Logan Place.

This collection of illusory paraphernalia has been culled from the history of London's premier magician's club.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

A bizarre house filled with an astounding array of collections.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

An eerie, derelict amusement park in Berlin.

A kaleidoscopic warehouse-maze of handmade neon signs.

Beggars were miraculously "cured" of their fake ailments when they returned home to this 17th century Paris slum each night.