Obscure SF: The chilling sign that still watches over Chinatown today FacebookTwitterEmail Old St. Mary's Cathedral, 660 California Street, San Francisco.Blair Heagerty San Francisco is a city of secrets. Some are buried, but some still form part of our daily landscape — curiosities that Bay Area folk drive, cycle and walk by every day. We're starting a new series today dedicated to digging into the stories behind those oddities. The first is an ominous sign that watches over a block right in the middle of the city that I've been curious about every time I've walked under its gaze. It's a message that has loomed ominously over passing San Franciscans going about their days in Chinatown for more than 160 years.