Fisherman's Wharf is a wonderful area of sights and smells. You name it in the way of seafood, and you can get it here.
Interesting architecture, bright colors, San Francisco Bay (complete with Alcatraz) and mountains in the background - what more could one ask for?
Flowers, that's what! And, of course, San Francisco has an abundance of those as well! A visit to twisty, turny Lombard Street provides an overabundance of gorgeous flowers.