Experience the legendary Alcatraz prison! It's a very interesting tour. Plus, you get to enjoy a ferry ride with an awesome view of the city. Tickets typically sell out a month in advance, so book your tickets ASAP.
Indulge in the "Ghirardelli Chocolate Experience", play a round of SF inspired putt-putt, grab lunch at the San Francisco Brewing Co., and then walk along the water to Fisherman's Wharf.
If you want to venture out for a walking tour of SF, head toward the Palace of Fine Arts. It is an architectural masterpiece and is located near Crissy Field and the Presidio.
A great way to see the bay and get your exercise in for the day! Ferry boats are available to take you and your bike back to SF.
Need a few more ideas? Check at this "tour de SF" with additional SF points of interest.