Ever since Bungie announced Halo, I have been getting as much information on the game as I possibly can. I have also been watching the movie quite a bit, and that is what this message concerns. (One thing, I am going to be talking about different frames in the movie, and therefore I have taken many screen shots, 14 to be exact, to help you with what I am talking about.
First of all, in picture 1, we see in the background an Eiffel tower-like structure beyond the atmosphere. This could be the ground sloping upwards in a circle shape. In picture 2, we see a pretty much identical structure in the background. If you were to put the two pictures together, we can see how this would be the second slope of the ring that was behind the camera in picture 1.
This second part concerns the first section of the movie, when the human is at a holographic control board of sorts. It appears as if beyond the control board there is a holographic projection of a large ring surrounding a planet (pictures 3, 4, and 5)... Notice the large orb that is in the background in a couple shots during the movie (6 and 7). This could be the same planet that is being projected in the hologram.
More appearances of the ring curving skyward show up in pictures 8, 9, 11, 12, 13, and 14. However, in picture 10, we see a dark line going across the sky. Since it is not an effect of the plane (foreground), this could very well be the opposite side of the ring, from a ground view. We can also see the planet in the bottom left corner of this picture (not marked), which further supports this theory.