This Budapest bar allows drinkers to leave their mark on the walls, floor, and even ceiling.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

Central Europe's largest collection of mini-bottles is on display at this museum devoted to a bitter Hungarian liquor.

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

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

An Escher-inspired library dedicated to the wonders of the human mind, yet closed to the public.

Need to book a room at the Hotel Pennsylvania? Just dial up 6-5000.

A restaurant and observation deck built in a unique broadcasting antenna.

Berlin's old airport.

Cold war icon and onetime "hole" in the iron curtain.

Amsterdam's Red Light District leaves little to the imagination.

Meet your friends, marry your true love, or tell your enemies to kiss your butt under this historic Pittsburgh timepiece.

This abandoned Belgian fortress is purposefully being left to nature.

This giant urban staircase was built to keep the city's brave fighting men from getting waylaid in the red light district.

This collection of over 50 murals celebrates Brussels' rich history as the self-proclaimed home of the "comic strip."

A little sculpture with a large wardrobe.

Three floors of musical instruments coming from all corners of the world and hundreds of years of musical history.

Petting this mysterious iron monkey supposedly brings good luck.

A visionary precursor to the Internet made of index cards.

A marble Lucifer hides behind the pulpit of this Gothic cathedral.