The plan was to hike the Dipsea trail, a delightful 7+ mile walk from Mill Valley, California to Stinson beach. Wikipedia says:
The Dipsea is well known for its scenic course and challenging trails.[32] The race starts on Throckmorton Avenue in Mill Valley, near Miller Avenue, in front of the old train depot (now a bookstore). After traversing a few blocks in Mill Valley’s downtown, runners climb 688 stairs[33] (now 700 stairs, after the renovation of the middle section in Nov 2017) leading up the side of Mount Tamalpais, and then pass through Muir Woods National Monument, Mount Tamalpais State Park, and the Golden Gate National Recreation Area.