I suggest you choose the Russian Ark, which is a bit biased, but it has distinctive features, mainly long shots. The whole movie is mirrored to the end, which is the longest long shot in history.

From these aspects, we can first mention some precedents of long shots, Soul Taking, and most of Beratar's works.

Secondly, it introduces the aesthetic theory of long shot and analyzes the advantages and disadvantages of this film. You can refer to Bazin's What is a Movie, which is not available online.

Third, the film is groundbreaking. First, its long lens is very helpful to the theme it expounds. As for its theme, you can read it yourself when you have time, but you can go to Wikipedia when you don't have time. Second, its technology is not filmed with film, but digitally recorded in a computer. Long shot, non-film and weak narrative can be said to point out a way for the future of art films.