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.

The "Fun Spot of the Desert" is now a haunting ruin, and a reminder that putting a water park in a desert is a bad idea.

The ghost town that ended up on Ebay.

This naturally heated mountainous creek has created a group of neon blue pools of potentially deadly boiling water.

Abandoned bridge hidden deep in the San Gabriel Mountains.

The final resting place of a space program monolith, soon to be unveiled again to the public.

This rare example of a "tidefall" is a spectacular drop from the cliffs down onto the beach.

The now-abandoned tunnels were built for the transcontinental railroad on the route where the first wagon train entered California.

Visible below the waves are memorials to the city's Gold Rush dead.

This Big Sur waterfall drops 80 feet directly into the Pacific Ocean, and inspired the hillside house up top.

Trails through lava-carved tube-caves display sparkling bacteria and a rich history.

Carved by a waterfall in a hard-to-reach rock formation, this heart-shaped rock has inspired romantics for decades.

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

Each year these high desert hills are absolutely covered with poppy flowers in a surreal show of nature.

A "gravitational anomaly" located in the redwood forests just outside of Santa Cruz, California.

Towering basalt columns, a creation of fire and ice.

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

The rocks in this arid basin leave trails of movement behind them.

A trash dump made beautiful by nature's power.

Hollywood's most famous landmark, the "temporary" sign that has stood for decades longer than intended.

A winding path built in secret on the edge of the continent.

Once thought to be the oldest living tree in the world, Methuselah was germinated before the Egyptian pyramids were built.