If you could travel back in time to see what the San Fernando Valley looked like 100 years ago, you would probably be disappointed. Dirt, dirt, dirt. And a lot of weeds that easily caught on fire. Yes, and a few Live Oak Trees. And in Los Angeles, you might be discouraged by the swampy conditions and the smelly black stuff oozing up from the ground. La Cienega means swamp, you know. And the La Brea Tar Pits weren't the exception, they were the rule.
But you can still see the native plants, undisturbed, just the way that the have been for thousands of years. But you gotta get off of the freeway. My suggestion is to go to the end of Malibu Canyon, which is right nearby where I am writing this now. It's the Las Virgenes Canyon Open Space Preserve in Calabasas.
And if seemed ugly to people 100 years ago, it's a breath of fresh air now.