I never noticed that Boudin Bakery at Fisherman's Wharf in San Francisco has a little self guided tour on the upper floor. It has some displays on the history of the company as well as information about bread in general and specifically the sourdough that they make here. There is also viewing area that looks down on the bakery floor. In particular, you can see where they keep the 150+ year old "mother dough" that is used in making their bread.