Where is the audition city when the venue is upi convention center?
CREATE TABLE "table1_28793672_1" (
  "episode_air_date" text,
  "audition_city" text,
  "date" text,
  "venue" text,
  "callback_date" text,
  "callback_venue" text,
  "golden_tickets" real
);
SELECT "audition_city" FROM "table1_28793672_1" WHERE "venue"='UPI Convention Center';