Beginner trail, good when you want a quick ride, the back portion does offer some single track with short steep climbs but those are optional. Watch out for walkers and horses as this is a popular trail for both.
North on 101 from Novato,take Atherton exit, head towards airport/park & ride, trailhead is on left 100 yards past park & ride.
http://www.singletracks.com/item.php?c=1&i=8100