A pair of slides and a tree-lined stair corridor have been an urban oasis for nearly 40 years.

A walk-in working camera obscura produces 360-degree live images of the San Francisco coast.

Olfactory delights in San Francisco's Botanical Gardens.

Relics of the 1894 Midwinter Exposition continue to delight visitors today.

Carnivorous plants, medieval aphrodisiacs, and the largest original wood structure glass conservatory in the western hemisphere.

Get lost in this haunting fairytale art walk through a man-made eucalyptus grove.

The only theatre in the world constructed specifically for sound movement.

A winding path built in secret on the edge of the continent.

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

A huge musical instrument played by the ocean.

An artsy hidden staircase leads to breathtaking views of San Francisco.

A psychedelic labyrinth on the San Francisco bay.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

This house's itty bitty size means no humans allowed.

A once-secret library of Freemason history in Catalonia.

The largest Art Nouveau complex in the world is a Barcelona hospital with a 600-year-long history.

A temple to modernity, tucked away amid Barcelona's more well known museums.

Every day is like Christmas on this street where the traditional Neapolitan nativity scene comes to life.

This magical-looking island is notorious for the misfortunes suffered by its owners.

An underground paleo-Christian burial site composed of the remains of several cemeteries and Basilicas.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

Nestled in the heart of Milan is a real wunderkammer of morbid curiosities.

Milan's duomo is covered in beautiful carving including a curious "dinosaur-like" beast.

This giant middle finger statue sends an unambiguous message to Italy's bankers.