Serene Velocity

Serene Velocity is a 1970 American experimental short film directed by Ernie Gehr. Gehr filmed it in the basement hallway of a Binghamton University academic building, using a static camera position and changing only the focal length of the camera. It is recognized as a key work of structural filmmaking and has been inducted into the U.S. National Film Registry.

Synopsis from Wikipedia, CC BY-SA 4.0. Everything below written here.