The loop is an infinite loop of reality planes, like The Sea.
From any reality plane, if you got on the top of one, you would see nothing but different versions and colorations of The Sea. The angle taken in the picture is as if you were above the loop instead of looking outwards.
Inside the loop, there are infinitely many combinations and types and colors of reality planes. Each of the black spots are rips where reality doesn't function properly.
The loop is contained by itself, as it loops itself infinitely. However, Theories of a hypothetical object called The oven suggest that the reason the loop is so cold is because it exceeds the 64 bit integer limit for temperature, thus heading back to negatives. This, however, has not yet been confirmed.