Behind this beachfront shop lies a spectacular, colorful sea cave with an equally colorful past.

This strange hill on Old Fort Road where gravity works in reverse has been fascinating locals for years.

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

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

An underground mansion with fruit-bearing trees and grapes growing beneath the surface of central California.

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