It is not the same on all sides as it depends on the desired proportion and alignments. The foreground border is probably 24" to 30" wide.

There are a lot of pictures on here of similar "step" ceilings. It can be achieved by either of the 2 following methods, both of which involve creating a border at the edge of the ceiling: (1) layering a border of 1/4" thick drywall over the drywall on the ceiling, screwing it into the ceiling joists, and then taping/mudding/sanding/painting the drywall seams; or (2) nailing mitered wood/mdf trim of the desired width into the ceiling joists to make a similar box border around the edge of the room; you then caulk and paint the miter joints. It's pretty simple actually, and adds a neat architectural effect. If you have low ceilings, you can paint the step ceiling the same color as the walls. It gives the illusion that the ceiling is higher.