Bay seniors hoping to walk off some of the weight gain from holiday partying can take an all day, cross-city hike on Sunday December 27. Starting at 11 am in Bernal Heights you will loop across SF’s major hills including Twin Peaks, and Dolores Park, covering over 13 miles including stairways, nature trails and mural-painted alleys. The trek is 13 miles long and ends at 5. You can bail out at any time. Free.