Under Weird California they describe the Forestiere Underground Gardens of Fresno. http://www.weirdus.com/states/california/personalized_properties/forestiere_underground_gardens/index.php
I can’t believe that these are now an official tourist attraction! During the years between Mr. Forestiere’s death and their opening to the public, we used to sneak out there and explore when we were in high school. These man-made caves were just in an old field. We’d take flashlights out there and explore all the passage ways and rooms. It was a good chance for the boys to scare the girls and to make up strange stories about this odd place. It was all in good fun, and we never told our parents. I can’t believe that the plants survived, because I don’t think it ever was watered, except for natural rain (which is less than 10 inches per year normally.)
By the way, they were way out in the country when I was in high school. Now they are in the center of the populated town.