Redwood Creek Challenge Trail is a playground in Grizzly Peak at Disney's California Adventure. While it's not a "must do," it is also recommended.
Think of this as "Tom Sawyer's Island" for bigger kids. This faux campground offers zip lines, cargo nets, forts and suspension bridges for exploration. Join Russell from Up and become a Wilderness Explorer by completing some of the challenges on the trail. Note that some challenges might have a height requirement.