Crissy Field (603 Mason St. at Halleck St., 415/561-7690, www.crissyfield.org, daily 9 a.m.–5 p.m.), in the Golden Gate National Recreation Area, is a park with a mission. In partnership with the National Park Service, ecology programs are the centerpiece of the Center. Check the website for a list of classes, seminars, and fun hands-on activities for kids of all ages. Many of these include walks out into the marsh beyond the center and the landscape of the Presidio and beyond.

Many people who like to hike, like to do it in some semblance of solitude. That can be tough to come by in the ever-crowded Golden Gate Park and Presidio. McLaren Park (Persia Ave. at Naples St., 415/239-7735) is something of a hidden gem in the busy City—an uncrowded park with miles of hiking trails, dozens of picnic tables, athletic fields, an indoor pool, and even a nine-hole golf course. You can enjoy a set of tennis, swim some laps, or play a quick round. But most of all, you can walk.

Seven miles’ worth of trails are asphalt paved, and plenty of undeveloped trails wend off into the brush and trees all around. If you’ve got the stamina, you can circle the whole park just by following its trails.

Feel free to bring your canine companion with you to this dog-friendly park. On the other hand, take care walking here if you’re a woman alone. McLaren Park is generally quite safe in the daylight hours. But at night it becomes much less safe, so plan to finish up your hiking, picnicking, and playing by sunset.