The Backbone Trail runs for about 65 miles through the Santa Monica Mountains, linking Point Mugu in the west with Will Rogers State Historic Park near Pacific Palisades. You do not need to hike the whole thing for it to be worthwhile: short sections give you ridgeline views, chaparral-covered slopes, oak canyons, and, in clear weather, sudden blue views of the Pacific.
For visitors based in Santa Monica, the eastern trailheads are the easiest taste of the route. Bring more water than you think you need, especially in warm weather, and start early if you are planning a longer section.