The world's first clock to use set theory as a measure of time required the invention of a new light bulb just to maintain its obtuse measurements.

One of downtown Berlin's last reminders of its Communist past.

A monument to the man who almost killed Hitler.

These brass bunnies honor the rabbits that dominated the no-man's-land around the Berlin Wall.

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

A silly medieval mural preserved on the side of a Viennese house.

The former private quarters and office of Dr. Sigmund Freud now hosts a museum housing the works of the founding father of psychoanalysis.

A tropical paradise just a short trip from the opera house is filled with beautiful winged creatures.

The beautiful baroque library of the Hapsburg empire.

A German town is growing a building out of trees.

Inside this German disco, visitors can take a literal ride on the dance floor.

Stuffed people arranged in unsettling scenes give a voyeuristic glimpse of life within a historic old hotel.

A trough of 700 strange bronze faces runs through a narrow alley in Ljubljana's old town.

A beautiful drive through the foot of the Alps traces the path of 15th-century Turkish raids.

This abandoned Slovenian military barracks has become a punky-political art squat.

This 1920s Dutch barge is now a floating bookstore.

This wildly-tiled artist's palace is a living and growing account of the creator's life, loves, and labors.

The site of London's first coffee house has been serving refreshments of one kind or another for 360 years.

The quaint little store that is said to have inspired a famous Dickens novel was only given its name after the book was released.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

A kaleidoscopic warehouse-maze of handmade neon signs.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

Germany's Glienicke Bridge has a shady history of clandestine meetings, espionage, and spycraft.