Explore San Francisco's parks and get some exercise in the process! San Francisco Recreation and Parks will be organizing and leading weekly free nature walks around San Francisco's many parks! On the second Saturday of the month, participants can explore Lake Merced! The lake is surrounded by a 4.5 mile trail, making it a popular spot for joggers. Super fun fact, Lake Merced has supplied water to San Francisco since the 1860s! Come explore the lake and its surrounding area, learn some more lake-related fun facts, and get some exercise.