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

A series of caves under Castle Hill that once held the prisoner Vlad Tepes, better known as Count Dracula.

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

A 19th century artistocrat's mansion, turned into a library, hidden in a modern library.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

This former insane asylum now holds a pathological anatomy museum.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

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

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

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

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

This Nazi ruin was the site where Hitler was almost blown up by a suitcase bomb.

Real bones which are said to have belonged to a Polish dragon.