I will be in S.F. for an afternoon meeting in the Civic Center on a week day later this month. I'll have about one hour for lunch before the meeting. Any suggestions for a wonderful restaurant within walking distance suitable for a single diner? I'm open to anything and everything--high end, low end, any kind of ethnic; I just would like to know if there is any restaurant in the area that S.F. Chowhounders believe is in the "don't miss this place" category.