It boggles the mind, but there isn't even a nothingness outside the universe. Space itself is supposed to be self-contained, and limited. Sort of like the earth, limited area, but no edge to fall off of. Space, limited volume, but no "edge" to nothingness.
Definitely boggles the mind. What Francis Schaefer called "nothing-nothing." He also described it as both necessary and unthinkable at the same time.