Chinatown in the City by the Bay is the biggest in the US. Once you step into it forget about America - shops and healing centers with signs in Mandarin, red lanterns, dragons and Asian paraphernalia. Better visit during the daytime - at night everything is closed. By the way, the famous fortune cookies you get with your receipt were invented here - you can visit the plant where they make it - on Ross Alley. As for food, watch where locals eat but it would be great if the place has an English menu. My choice is Peking duck - they know how to make a good one. The food is cheap and good contrasted to souvenirs - expensive and made in China in the worst meaning of this expression.