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 randomness of this wall of lava lamps helps encrypt up to 10 percent of the internet.

Visible below the waves are memorials to the city's Gold Rush dead.

A modern mechanical planetary system, part of a 10,000 year clock.

A collection of 20th-century automata, penny arcade games, and musical contraptions.

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

San Francisco's newly reopened hands-on science museum.

Tiki luxury on Nob Hill.

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

A museum befitting the city responsible for supplying the majority of the world's LSD.

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

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

This shop specializes in oddities and Victorian-inspired wonders.

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

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

A psychedelic labyrinth on the San Francisco bay.

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

A huge musical instrument played by the ocean.

The world's largest sticker ball weighs in at a mighty 231 pounds.

A collision of human error and natural geothermal pressure created this rainbow-colored geologic wonder.