EDIT: In the game files I have found Phinis Gestor mentioning a very interesting theory in one of his lectures. Don't know if you can actually see it in the game, but it is very interesting indeed:
"It has been proposed that the object is in fact the entirety of Aurbis in one physical space. This would of course mean Tamriel, indeed all of Mundus, is actually contained within the sphere. It further suggests that we are somehow then outside our own existence while looking at it. While the idea seems dubious at best, it has not, at present, been entirely ruled out."
Reminds me of
The Eyes of the Overworld by Jack Vance. While working on the huge construction site of the wizard Pharesm, our impoverished antihero Cugel finds a small gelatinous creature, spheroid with many transparent tentacles.
A new thought occurred to Cugel. The creature displayed qualities reminiscent of both coelenterate and echinoderm. A terrene nudibranch? A mollusc deprived of its shell? More importantly, was the creature edible?
He decides the answer is yes. takes the opportunity to grill it over a fire and eat it. Unfortunately, this little creature is actually the goal of his employer's 318-year long magical-architectural project:
Pharesm drew himself to his full height, glared down at Cugel. The " 'creature,' " he said in a grating voice, "is TOTALITY. The central globe is all of space, viewed from the inverse. The tubes are vortices into various eras, and what terrible acts you have accomplished with your prodding and poking, your boiling and chewing, are impossible to imagine!"