6 - Structural beams are outside instead of inside.
You will notice when you approach the massive building the contains Space Mountain that there are concrete structural beams on the outside of the building. This isn’t at all a usual practice in most construction plans because builders want to conceal the structural components within the inside of design so that the outside is more appealing. So this made the design very unique. One of the main reasons for doing this when constructing Space Mountain was so that stars and lighting could be displayed on the ceilings and walls as part of your space-like transportation. You need smooth surfaces in order to really pull off the effect, and the supports would have taken up space on the inside and prevented a smooth surface.