Twenty-five years ago I first saw the wall at Battery Mendell, a reinforced concrete gun emplacement, completed by 1905, to guard the entrance to San Francisco Bay. It is situated in the Golden Gate National Recreation Area, north of the bridge. In the bright sunlight one could count the generations of paint, blue, grey, brown, gold, each taking turns to escape the surface whose hold was becoming ever more tenuous. The wall fascinated me, and I wondered what I could do to portray it without succumbing to the cliché of peeling-paint photography.