You can hang out at Fort Funston in San Francisco all day and watch hang gliders go by. This was an especially weird day to be an observer: the sun broke through park of the clouds in a circle, which makes it appear as though the glider is about to go straight through the hole.
If you have a dog in San Francisco or anywhere in the Bay Area, you must try Fort Funston. It's like dog heaven! There are dunes to chase crows on, beaches to chase balls on, and plenty places to walk. ALL OFF LEASH!!! Woof!!! My favorite activity to do is hike south from the parking lot on the top of the ridge. The view is beautiful and it is almost entirely empty. (See photo of Tora and the ridge)