Why settle for just one educational promenade around this history-packed, pedestrian-friendly city when you can choose from dozens? City Guides offers free walking tours on every sort of subject: Pacific Heights mansions and Alamo Square Victorians; the murals of Coit Tower and the Mission District; a meander through the Palace Hotel, the Haight-Ashbury, or across the Golden Gate Bridge; a stroll past Maiden Lane's long-gone brothels and boardinghouses. Since 1978 the volunteer guides have been leading these informative walks around every corner of the city under the sponsorship of the San Francisco Public Library. Over a hundred tours are offered every month; pick up a schedule at any library branch or visit the Web site, choose the tour you want, and show up at the designated place and time. (Reservations are only required for groups of eight or more.) Tours last an hour or two and proceed rain or shine; many are wheelchair-friendly. Donations welcome.