This massive redwood tree has a hole in the base big enough to drive through.

Only known mainland rookery of the threatened Stellar sea lion.

A collection of colorful dinosaurs hidden in an actual rainforest.

This ultra-modern California span is actually a titanic solar clock in disguise built by famed architect Santiago Calatrava.

340 bicycles, 65 feet high.

An institution that preserves the history of institutionalization.

A monument to the love people have for their pets.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

This Oakland fairytale kingdom, fiercely devoted to childlike whimsy, was an early inspiration for Disneyland.

A working model of the entire San Francisco Bay and much of the Sacramento River Delta, complete with regular tides that change every 14 minutes.

Concrete strongholds stand guard over the Golden Gate.

An amazing collection of fantastic reptiles, amphibians, spiders, and insects.

Seven ceramic sculptures are scattered around this California college campus.

This museum boasts the ninth-largest collection of insects in North America.

Come for the records, stay for the retro pinball machines.

The perfect spot for a picnic, right next to a giant ballistic missile.

The former Naval shipyard is open for exploring - mostly.

Frank Lloyd Wright died a year before construction on his largest public project even began.

'Cause the fence start shaking, the earth was quaking.

A raised boardwalk winds through a thicket of stunted, century-old trees no more than nine feet tall.

The largest drain hole in the world.

This abandoned boat was left in place thanks to its rotting beauty.

The haunting ruins of Jack London's dream house.

Nursery with extensive collection of flesh-eating plants operated by the author of "The Savage Garden."