A tree grown from astronaut seeds which were exposed to cosmic rays.

An unassuming grey box sitting on San Francisco's Pier 17 is a "sky diary" of the coastal city's temperamental weather.

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

A brooding mansion of clinker brick stands out among the Victorian houses of Pacific Heights.

The first AIDS memorial chapel in San Francisco and one of only a few in the U.S.

The largest permanent Monopoly board makes one of the longest games even bigger.

A statue commemorate Tommie Smith and John Carlos's brave protest at the 1968 Olympics, a watershed moment for civil rights.

At the base of the Golden Gate Bridge, a small sign basically begs for a high-five.

Once the largest windmill outside of Holland, with enormous 114 foot sails.

The key to turning shifting dunes into the green oasis of Golden Gate Park.

A pair of mutilated bronze octopuses slump at the base of the monument honoring California's admission to the U.S.

A masterpiece in Golden Gate Park by virtue of the artist’s debt.

A mysterious painting of the self-declared Emperor of the United States watches over a local hof-brau.

The remains of a 12th-century chapter house in Golden Gate Park.

A promotional sun clock on the site of San Francisco's great raceway.

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.

With the touch of a button, you can read a randomly selected short story.

The stones that traveled from Spain to eventually become a holy place for San Francisco's nature worshippers.

Golden Gate Park's historic collection of plants.

Gold Rush-era tombstones line the park's paths.

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

An overlooked and unassuming engineering marvel.

This concrete tangle of square pipes has stood as a proud thorn in the city's side since the '70s.

A hidden subterranean installation offers a view of the sky.