I just found this article you might be interested in. I thought the backdrops were always CGI, but to save time and money they used what's called "matte paintings" in the movie industry. Here's an example:
I also found out that some angles of the Liberty interior were shot in the Bradbury building in Los Angeles, but most scenes were shot in studio, in a "Bradbury stand-in". In the studio...
And here's the real thing, the Atrium of the Bradbury:
Read the entire article here. I found another cool site here: Just compare: