This is one of my favorite short films of all time and should be required viewing for all film pros and aficionados. It was shot in 1976, already astonishing for its time, and the title of the film is at the end. The caption at the beginning reads: "The film you are about to see was shot without any editing or speeding up".
I could say much much more, but I'll let the film speak for itself:
When you're done watching it—and not before—go visit the imdb trivia page here. And if you understand a little French, you can see the making of it here.