A few things. I seem to recall reading that the stage where the bridge was had a sloped floor, which caused platforms to have to be built to get the set level. Maybe that's in The Making of Star Trek? If one of the stages had a sloped floor, that might explain the step down at the end of the corridor. (Just where is this seen?) As to the bridge, they just rotated the command module by one step (half platform), not moved the bridge walls. They moved said module around when the camera was pointing at the viewscreen, but in other views you can see it's not pointed at the viewer (link) and, as pointed out above, you can see that the railings are not all the same length as the one by what would become Scotty's station consists of 3 segments and the one clockwise from it has only 2, which gives away that they're cheating the layout somewhat. Actually, if they DIDN'T move the sets around after "The Cage", which is more likely [EDIT: Actually, they did, as I reported in this post (link)], then the transporter room should be the door on the right when facing down the corridor towards the briefing room, not the left as draw here. UPDATE: According to @Harvey, from the production docs it looks like all the Enterprise sets were on stage 15, and all the Delta Vega sets (int and ext) were on 16.