The hidden lair of an alchemist rediscovered in a 2002 flood.

A Jenga-style cylindrical tower of books that appears to go on forever.

Countless grotesque faces stare out from this eerie Prague art wall.

Walk through Czech history in Prague's largest graveyard.

The history of occult science is turned into a creepshow at this lurid Prague tourist attraction.

Two stunning 17th-century libraries and a cabinet of curiosities.

Macabre astrological automaton clock dating to the late 1400s.

San Franciscans leave gifts and messages for the magical beings that live behind the tiny, mysterious door installed on a tree in Golden Gate Park.

The oldest burial ground in the city, final resting place of city founders, Ohlone natives and murderers alike.

In this century-old literary safehouse, print is alive and well.

The tea room that pushed the boundaries of adorable straight into...we can't find the words.

A 140-year-old castle with underground caves hidden in San Francisco.

A beautifully eclectic mix of architectural styles.

An ancient passage filled with stalls selling used books, once frequented by Vincent Van Gogh.

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

This historic Amsterdam bar used to accept sailor's monkeys as payment.

The history and future of cannabis.

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

Cat art as far as the eye can see.

A floating cat sanctuary on an Amsterdam canal.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.

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

A crumbling World War I fort that is reached through a series of concrete tunnels.

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