When not scavenger hunting in the city limits, it's nice to escape and explore the nature surrounding Los Angeles. If you've done one too many walking hikes, it may be time for you to head out on a mountain bike and explore! There are plenty of fire road trails for beginners, or if you're me--attempt a single track with lots of stopping and walking when it gets too scary.
I've always been impressed by The Backbone Trail. It's a ridgeline trail along the Santa Monica Mountains that extends over 65 miles! Don't worry, you don't have to hike/bike it all in one day. One summer we rode pieces of the trail that allow mountain bikes several times in attempts to cover as much ground as we could. Talk about a peaceful experience! We would see one or two people the entire trip, almost unheard of in Los Angeles. The trails themselves offer amazing views of the Pacific and almost constant ups and downs.
If you've done the trails on the "best hikes in L.A." lists, drive up to Malibu and try any portion of The Backbone. Bonus, on your way back home you can stop at Malibu Kitchen for an amazing sandwich to replenish those calories you just burned!