Nothing. The observer is key.
Please take a sheet of paper and draw two circles:
Let there be an one dimensional animal called the observer-1, which can only distinguish inside/outside. There is only one circle to be seen by observer-1. Let there be us — the observer-2 — who is able to observe the 2D world with that strange animal observer-1 either inside or outside a circle.
What do we see? 😉
[See this previous post for context.]