The empty lot at Harrison and Fremont streets is nothing much to look at, a football-field-long slope of dirt and weeds that greets drivers exiting the Bay Bridge into San Francisco. But a quartet of local designers see something else: a site that could become a sculpted realm of green folds spiked by artistic birdhouses - an evolving semi-natural terrain up to the moment when the 41-story tower slated for the site someday is ready to begin construction...more