I think it's missing some. There are a couple of hotsprings off the highway between Ventura and Ojai. They're 'wild' and completely natural - you can make your own pools using rocks and sand for dams. I saw Steven Spielberg once when I was there with a few people - he was reminiscing with another guy about the problems they had filming something...

Edit: I think it was empire of the sun. They were talking about how difficult it was to film explosions in Japan.

Maybe you’re thinking of Letters from Iwo Jima? They shot on location but the island is basically a mass war grave so they couldn’t use much pyrotechnics to avoid disturbing the ground.

Empire of the Sun was mostly shot in Shanghai and Spain. That was the one where they got fined for burning old tires for the special effect smoke, which dumped a bunch of toxic smoke on Shanghai.