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

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

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

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

The world's first zoo for microbes collecting the horrible and wonderful things living on and around us.

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

This shop and gallery is a modern-day cabinet of curiosities, unassumingly positioned along an urban thoroughfare.

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

The cedar tree in Highgate Cemetery earned its title by accident.

The streets of a sleepy Spanish town proudly exhibit some of the world's finest graffiti.

Fonts are born and bred here at the oldest letterpress type foundry in the United States.

Its town washed away centuries ago, this lonely tower by the sea tells the tale of a mermaid and a curse.

Hamburgers are intensely proud of their tunnel beneath the river.

An elegant chandelier hangs over this ancient sewer chamber, now open for concerts and public tours.

Owned by no one but beloved by all, Brownie was a good dog.

Hundreds of hopeful gold miners came here to get rich, but only two years later the small town was deserted.

Colorful umbrella-covered trees in Singapore's Little India look straight out of Dr. Seuss.

An absolutely beautiful 200-foot stained glass installation traces the evolution of knowledge.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.

Trace the history of writing at this unusual North Carolina destination.

A restaurant modeled after feudal Japan, where the waitstaff are trained as ninjas.

This network of tunnels housed an entire village for years, and even had a hall for screening movies.

La Monte Young and Marian Zazeela's "Dream House" will immerse you in an ever changing world of sound and light.

On Japan's Tashirojima Island, cats are king.