Surrounding Lake Perris in Southern California near Moreno Valley there are a number of trails that are not exactly fun but, there are a few hills that are challenging and the scenery is rather nice if you enjoy wide open spaces. Often I will ride the various trails until I am nearly exhausted. Then I will ride downhill to the lake. There are restrooms with water fountains. The water is clean and surprisingly cold. Great for refilling your water bottle or camel backpack. After refilling I have on hot summer days taken a dip in the lake. There is a specified swimming area with several lifeguards. Surrounding the lake there is an area for picnics with fire pits. To bring a vehicle to the park requires $10 for a car to start so bring you California Adventure Pass.
I generally park outside the park for this reason. Besides there are a number of trails near the neighborhood before the park that lead to the park from the outside that are an...okay ride.