I've got an afternoon to myself in SF coming up and I have no idea what to do with my time. I've been before so I've seen a lot of the major touristy things. My husband will be joining up with me at 6pm so I also don't want to do anything he'd feel really bummed about missing or that would be better to do with him. I'm staying near the Embarcadero Center. I'll have a car, but also love walking and am comfortable walking long distances. Any fun ideas?