Human-made caves excavated to hide a secret society of wealthy pagans.

A petite castle folly in the English countryside.

The gravestone of a delicate singer-songwriter bears a fittingly introspective epitaph.

This beautiful "lagoon" is actually a toxic soup filled with cars, carcasses, and trash. When warnings couldn't stop people from going for a dip, the town dyed it black.

Cemetery established by the Victorians as a solution to the overflowing graveyards.

The only university zoological museum in London houses extinct animals, bizarre natural history specimens, and a Micrarium of microscopic creatures.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

The largest of London's subterranean rivers and once a mad, bad center of London life.

A hands-off space for graffiti artists to hone and display their skills.

Residential building on the Regents Canal is a breeding ground for creativity and innovation.

Handmade treasures from around the world.

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

Dive bar built out of the remains of a whaling ship.

A living time capsule of the 1960s Richardson Bay water-front.

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

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

Named after a bandit and the star of several Hollywood prehistoric landscapes, these sandstone formations are a historical part of the Los Angeles natural landscape.

A treasure hunter's tiny bar, harboring celebrities since 1959.