Since moving to San Francisco from Seattle a little over a year ago, I've learned about the city on bike as opposed to by car or public transportation. Out of necessity, I've become familiar with the city's extreme topography (there are a few hills I actually walk my bike down) and its often confounding street layout. The city's history of fires and earthquakes lends a dramatic flair to what's underfoot (or wheel) and there's a definite sense that one's environment is not necessarily what it seems and could disappear at any moment. This Sunday, public artist Ledia Carroll restores a bit of lost topographical history through the inaugural event of the Mission Lake Project. The project begins with Carroll chalking an outline of Mission Lake ( a.k.a. Lago de los Dolores or Lake of Sorrows, where Mission Dolores got its name) a former freshwater lake that has long since vanished due to a combination of both natural and manmade causes. The chalking is followed by a bike race along the path with stops at historic markers and the day concludes with a barbeque on the lake's "shoreline." As part of Southern Exposure's yearlong Offsite series of public art, the Mission Lake Project illuminates the ways landscapes become transient. Southern Exposure's Mission Street Storefront gallery features maps, drawings, resources, and related ephemera from the project and in November and December, Carroll will lead guided tours of San Francisco's hidden underground waterways.