Although not formally part of Golden Gate National Recreation Area, Muir Woods is just a hop from the Marin Headlands, and definitely worth the trip. This is one of the most dramatic and accessible old growth redwood forest along the California coast. Not visiting Muir Woods while you're here would be like visiting the Grand Canyon and not peaking over the rim. The towering old trees and the distinctive and lush ecosystem make this one of the most special places on the planet. Trails cross lands owned by many different public agencies.
Many trails are steep.
Wear clothing you can adjust. Fog and winds are usually heaviest at areas closer to the Golden Gate, especially during the summer. Fall brings the best weather. The ocean is always dangerous and swimming is not advised. Those fishing or walking on the rocky shoreline can be swept off by a sudden large wave or trapped by the incoming tide.