Mount Tamalpais was a challenging but beautiful hike and a great workout.  I really enjoyed how the trail varied from rolling hills, to lush creaks, to a redwood forest, through campgrounds, and finally ascending to the peak of Mount Tamalpais.  The views of the ocean and San Francisco Bay along the way and at the peak were amazing and well worth all the work to get there.  The trail system is more like a net than a direct trail and we strayed from the planned path and although we were able to find an alternate trail back we ended up hiking more than planned for a total of 19.72 miles.  We returned to Stinson Beach after dark and were completely exhausted but glad to find many people enjoying the beach and the town after dark.  Make sure you leave yourself plenty of time and bring lots of water.