Griffith Park is the largest city-run park in the United States, covering more than 4,000 acres in the Hollywood Hills. It remains a largely rugged, natural space. It is accessible via several entries through the neighborhoods at the foot of the hills. Come here for a day of hiking and picnicking: hiking maps can be obtained from the Ranger Station (4730 Crystal Springs Drive).
During the busy summer season, the Griffith Park Observatory -- the park's biggest attraction -- is accessible only via shuttle, and you need have a pre-paid reservation. (Call the reservation hotline at 1-888-695-0888 to reserve a shuttle spot and pay for entry to the observatory itself.) Once inside, enjoy the public telescopes and sit in on a fascinating planetarium show.
Griffith Park is also home to the Los Angeles Zoo, the Museum of the American West, and the beautiful, open-air Greek Theater.
URL: http://www.lacity.org/rap/dos/parks/griffithPK/index.htm