San Francisco's urban bison herd has persisted in the face of extinction, development, and disease.

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

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

The one-time watch house for incoming ships at the Golden Gate now stands abandoned and hidden in trees.

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

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

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

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

A huge musical instrument played by the ocean.

This shop specializes in oddities and Victorian-inspired wonders.

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

Hordes of precariously balanced stone figures crowd the shores of the Hudson River.

Long the exclusive domain of birds and vagabonds, this little-known Central Park peninsula is open to the public once more.

Wine bottle sculpture with a ship's stateroom inside.

Lie in a hammock where George Washington stood.

This abandoned subway station can still be seen on regular commuter trips.

The beautiful tunnel that ran from the lobby to Penn Station is still hidden underneath 34th Street.

Unlock the secrets of the conjuring arts.

A celebration of capitalism in Midtown.

A hands-on traveling collection of the innovative devices of yesteryear.

A New York garbage depot holds a secret collection of weird and wonderful refuse.

A Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

The feral felines of Roosevelt Island have a small army of allies and an abandoned hospital all to themselves.

A semi-scholarly approach to sex.