A must for fans of The Maltese Falcon in particular and film buffs, in general. For others, it is an interesting look at what San Francisco was like in the late 1920s and early 1930s. The tour, which explores the posh heights of Nob Hill to the less exalted Tenderloin, hits all the spots that are in the classic film. It lasts about four hours and is three miles long. Meet on the steps of the Main Branch of the Public Library (between Fulton and Grove streets). No reservations are required. Look for the guy in the trench coat. Cash only.