Grab a snack, some wine, and have a seat in the park. If thats not your thing then take a walk around the giant dome, smell the flowers and take in the view. After you've seen all you can take a short walk over a few blocks towards the art district and pop into one of the many galleries that line the street.
Also, the library on the grounds offers free movies on friday nights. I happened to catch a Hitchcock film during my visit.