A unique piece of graffiti offers a little slice of local history and mystery.

This mysterious series of teeny guerrilla installations sheds a whimsical light on street art in Oakland.

Julia Morgan's Moorish-Gothic labyrinth of fountains, trees, natural light and Oakland's notable dead.

A tiny theater hidden in an alley plays a constant stream of short silent films for anyone willing to peer through the peephole.

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

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

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

The oldest cemetery of modern-day Athens blends the modern and ancient worlds.

A beautiful mountaintop mausoleum devoted to a Montenegrin icon can't seem to make everyone happy.

The "dragon babies" of southeastern Europe.

A miniature train-ride through Slovenia's largest cave system.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.