I must see if you have never visited San Francisco. A bit touristy, but you can't come to SF without seeing Pier 39.
This is where famous poisoners, like Al Capone were sentenced. This tour is worth the visit, but you MUST book your tickets well in advance.
The name says it all! You have to see this!
If you have an extra day, you can take a drive to the famous Napa Valley Wine Country. There are some amazing wine tours you can book in advance. Only an hour away.