Trivia: X-X "The Lost Episode": Some other character cameos in the concerto audience include the two English ladies talking about fish in "Revolution", and Dr. Victor Payten, his interviewer, and the soap opera character Rebecca from "Episode 257-494".
Trivia: X-X "The Lost Episode": Character cameos: In the concerto audience you can find Mad Mod, Slade's former butler and the former HIVE headmistress. Also, the conductor appears to be Mumbo in his non-sorcerous form ("The Sum of His Parts").
Trivia: The Red Chef who frequently appears on TV is a parody of Iron Chef French Hiroyuki Sakai, one of the two chief cooks in the discontinued Japanese cook show Iron Chef, which specialized in French cuisine.
Chosen answer: It is located in California, as shown in "Teen Titans: Trouble in Tokyo". Possibly San Francisco as seen in the comics.
MasterOfAll