Dark Days is a documentary about a group of homeless people who live underground in abandoned subway tunnels in New York City. It was shot entirely on film by the director and the homeless people in the movie. None had any previous film experience. It is one of the most impressive achievements in filmmaking I’ve ever seen, a surreal and compelling documentary. The “making of” bonus material on the DVD completes the story.
From the linked DVD Talk review: “Dark Days is an alternately humorous, saddening, touching and fascinating picture that is a masterful documentary of the lives these people lead and the hope in their hearts for a better life… This is a powerful, emotional picture that is an amazing effort from director Singer. It’s definitely a must-see film.”