Theories by Forgingiron.
Loop Theory (debunked)
I think the Loop isn't just a trap; it's the actual Submachine. The other locations you see: the temple, the basement, and other locations, are just the spaces between the locations. But when you saw the Loop in its true state, it was like being transported into deep space. Compare it to Subspace from Super Smash Brothers Brawl. It has the normal-looking locations, and it also has the eerie scifi-like locations, Subspace. The Loop is the equivalent of Subspace, or rather, vice versa.
But what about the looping traps of coordinates 690? That is just another location, like the basement or the temple. And the perpetual locations, like those at 555, 006, 917 and 923? Those are unknown. They have normal scenery, but not the Loop's physics.
The portal in the center of each loop "level" is the center of the Subnet. The Core is close, however. The Loop does not fall of any of the seven layers. It's the eighth layer, the mysterious driving force behind the Subnet's very existence.
And finally we come to the mysterious corridor in 747. That is like a gateway to the Loop, only it's not to the actual Loop. Take the "deep space" simile I mentioned previously. The endless corridor is like exiting our atmosphere and plunging into space. Either that or Murtaugh did something funny with his karma arm.
In conclusion, I would say this: The loop is space. It's the glue which holds the coordinated locations together.