Upon boarding one of these mega ships, the size plays tricks with your mind. Seeing a carousel in one little section doesn't help.
I took this photo on the Oasis of the Seas last year. I was looking down from about eight decks above. And, there are another eight decks below that. So if your mind gets a little blown at the beginning, chances are it will last all week; which is about how long it takes to find your way around.
These ships would be impossible without a lot of elevators. Of course, with the amount you eat, it would be healthier to take the stairs. However, when entering a reality bubble, the standard rules and concerns don't apply. At least that's how it works for me.