East of Napa, the Skyline Wilderness Park spreads over two rolling mountains and has a range winding mountain biking singletracks totaling 18 miles. A good starter route begins with a 600 feet vertical climb up old Lake Marie Road for 2.5 miles up to the lake. Then follow the singletrack counter-clockwise around the lake. Continue up the Skyline Trail to the valley overlook and continue on for the 4.5 mile rolling descent back. More? Try ascending Sugarloaf Mountain via the Rimrock Trail over 1200 vertical.
To reach the mountain biking trailhead from Napa on SR29, exit onto Imola Avenue heading east to its end.
Overall, Skyline Park is the 23rd most popular mountain bike trail of all 132 mountain biking rides in California.