While Gotham City Burns (2) - S1-E30
Continuity mistake: While Bookworm is at stately Wayne Manor he hands Aunt Harriet a book, and when she opens it Harriet and Alfred are gassed unconscious. In the next closeup of the rare book encased in glass, its open pages have colorful illustrations, but in the next shot the open pages have only plain text. (00:09:30)
Answer: There wasn't one singular city used. It was shot in and around various locations in California, plus on a lot of sets and backlots. Ex. Some scenes were shot in LA, some in Pasadena, some in Santa Barbara, etc.
TedStixon