From Thinkwalks:
A natural and cultural history of the bike route through the Lower Haight neighborhood. Covers water flow, dune and hill reshaping, and the bike politics of recent years. Lots about the Native American village that was here and about how the area looked before it was streets. Meet at the bike mural (Church and Duboce), end near Alamo square. 2 & 1/2 hours.
