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.

A museum befitting the city responsible for supplying the majority of the world's LSD.

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

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

A psychedelic labyrinth on the San Francisco bay.

Far from the shore, this sandy victim of the Skeleton Coast looks like it was plopped in the middle of the desert.

Happy harbor seals frolic and snooze on this warm, sandy stretch of coast.

In Portugal, a secluded stretch of untouched natural beauty hides at the bottom of a steep hill.

These old World War II fortifications have been transformed into an unusual equine attraction.

A mostly desolate bar on a remote island hosts hundreds of sailors for a few days each year.

A beach made of semi-precious green sand on the Big Island of Hawai'i.

Living fossils in this remote Australian bay provide a glimpse of what Earth may have looked like 3.5 billion years ago.

An ancient capital city that dates back 3,000 years old and harbors many surprises.

The largest earthwork effigy in the world.

Roots and stumps that lay inundated for two millennia are on display in Japan's city of three mysteries.

The meteor that sealed the fate of the dinosaurs landed at this site, one of the largest impact craters in the world.

The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

Step into the cool deep past and unknown future of who begat who.

Native Americans built this circle of stones, which was used to predict astronomical events.

Home to Hollywood history and a very special salt crystal.

One thousand trees were planted in Norway to be used to print books a century from now.