The Santa Monica Mountains, which extend from the Hollywood Hills north into Ventura County, include many great hiking trails. Here is a picture from the 7 mile loop to Sandstone Peak, the highest point in the range:
This hike features unusual sandstone formations and sweeping views over the mountain range, the valley, the ocean, and the Catalina Islands. Below is a map with driving directions from downtown L.A. to the hike's trailhead. The Modern Hiker blog has more pictures and information about this hike and many other hikes in the L.A. area.
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