Natasha Simons, at the new-to-me Mary Sue (“A Guide to Girl Geek Culture”), sheds some light on the context of the end of the silent era.
She seems to see the character of George Valentin as most closely based on William Powell, on the evidence of Jack Russell terriers, which seems off base to me. Valentin is collaged from the lives of several silent stars, including Douglas Fairbanks and Valentino. His character design is fascinating, by the way, not least because the actor who portrays him, Jean Dujardin, bears an occasionally uncanny resemblance to both early 1960s Sean Connery and Clark Gable.
I had thought sections of the film set in the city were shot on the old RKO Pathé backlot, the “40 Acres,” which was used to provide settings for downtown Mayberry and city settings for at least two and I bet more episodes of Star Trek, but that backlot appears to have been torn down. If I come up with a locale I will post it.
UPDATE: here is some info on locations. Warner Bros backlot and, it seems, Pickfair!