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

Its buzzing collection honors vibrator history.

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

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

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

Olfactory delights in San Francisco's Botanical Gardens.

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

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

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

A shop full of natural curiosities, carnivorous plants, and costumed taxidermied mice.

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

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

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

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

A psychedelic labyrinth on the San Francisco bay.

The world's first clock to use set theory as a measure of time required the invention of a new light bulb just to maintain its obtuse measurements.

A fascinating insight into daily life in the Eastern Bloc.

From toys to kettles to scientific instruments, this German museum celebrates the beauty of 20th century design.

A museum dedicated to a Cold War era sausage.

An eerie, derelict amusement park in Berlin.

A collection of abandoned typographic signs from Berlin and beyond.

A museum dedicated to the history of a terrifying secret police is now held in their former headquarters.

On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

The most visited, and possibly most controversial, museum in Germany.