The bedroom pictured below, from the film, doesn't have any doors, only a door to the bathroom.
Everyone thinks the monolith is from Aliens, it might be, but I don't think so. Aliens are never mentioned a single time in the film. The only instance of "alien" talk is during a meeting in the beginning of the film where the director mentions "intelligent life form."
The monolith shape is found throughout the film. Everything you look at is monolith shaped; well not everything, but a large portion of the film as rectangular objects. Kubrick even uses the monolith and 2001 "Easter Eggs" in other films. Like the burning monolith in Full Metal Jacket. Kubrick also uses the 7 diamonds you see at the end of 2001 in other films as well, including Full Metal Jacket, again.
Kubrick was a perfectionist, every thing is always centered (one-point perspective), but in this film he not only uses one-point perspective, everything always tilts 90 degrees. Even the monolith, the only time you see it when it is not vertical, it is floating in space at a 90 degree angle. Genius! So my question to you is, what the fuck is the monolith? Where did it come from?
Some people have the theory that it is a theater screen and we are looking at ourselves. The film originally had images being displayed on it; but, Kubrick removed them from the monolith because he didn't want it to be thought of as "an advanced television teaching machine," so what is it then?
The film God, Roger Ebert has some theories; http://www.rogerebert.com/rogers-journal/2001-the-monolith-and-the-message
"Q. What's that big black monolith? A. It's a big black monolith.
Q. Where did it come from? A. From somewhere else.
Q. Who put it there? A. Intelligent beings since it has right angles and nature doesn't make right angles on its own."
Another terrific source, and someone who has put a lot of these 2001 ideas into my head is Roger Ager; http://www.collativelearning.com/2001%20chapter%202.html
image via; https://goo.gl/BOEY89