I love stumbling on places like this – totally unexpected. Just 2 blocks from City Hall is the 1928 gorgeous Beaux-Arts building that houses the Wells Fargo History Museum. This small (FREE) museum has videos, displays and hands-on exhibits detailing the history of Wells Fargo and Westward Expansion in the 1800’s.
Highlights include a replica stage coach (great for photo ops):

And a display of gold nuggets:
If you have any actual banking to do, the teller area in the lobby is gorgeous and has an authentic stagecoach:
Tobey says: Blah….NOTE: The museum is closed on weekends.