Possibly the best documentary about Chaplin is The Unknown Chaplin. In three parts you can watch here it captures the cinematic genius as he was never meant to be seen. Using countless reels of rushes, outtakes, and abandoned films Chaplin had wanted destroyed, film archivists Kevin Brownlow and David Gill have meticulously crafted an essential and fascinating documentary homage to the Little Tramp who will no doubt keep us laughing until the last flickering frame.
We suggest that you watch The Unknown Chaplin after you see City Lights.