On today's Milton List, a link was provided to the cosmic vision above.
That sounds rather grand, I suppose, but I'm merely referring to the sketch of Milton's 'cosmos' at the top of this post, which I've borrowed from D.F. Felluga's Purdue website -- specifically, the pages for his Fall 2000 course on "Great Narrative Works," which must have been a very interesting course indeed. Take a look for yourself.
Anyway, as I noted, the link was provided on the Milton List, and one of the list members posted a note that leads me to believe that Felluga borrowed this image from Merritt Hughes's edition of Milton's Complete Poems and Major Prose, on page 180 of the 1957 edition (New York: Odyssey Press). Perhaps someone could confirm this?
While I love sketches of this sort, I wonder how accurate it is. As Dennis Danielson remarked concerning the term "Cosmos":
[T]hat whole cosmos ("this pendent world") is an almost indiscernibly small point of light when viewed from far out on the fringes of Chaos. Thus we need some word more encompassing than "cosmos" to describe Milton's heaven, hell, chaos, and (relatively speaking) tiny cosmos.I agree. The image above is far more than the 'cosmos'. Moreover, it makes everything look rather 'round', whereas Milton seems to depict something indescribable by any limited three-dimensional shape. Chaos, for instance, would seem to extend indefinitely down, as suggested here in PL 2.890-897, where Satan, Sin, and Death first glimpse chaos:
Before thir eyes in sudden view appear Chaos would seem to extend far below the region of hell, for after Satan finally steels himself to brave the dangers of chaos and leaps into the abyss, he soon finds himself plummeting downward:
The secrets of the hoarie deep, a dark
Illimitable Ocean without bound,
Without dimension, where length, breadth, & highth,
And time and place are lost; where eldest Night
And Chaos, Ancestors of Nature, hold 
Eternal Anarchie, amidst the noise
Of endless Warrs, and by confusion stand. (PL 2.890-897)
...At last his Sail-broad VannesA "league" is about three miles, and a "fathom" is about six feet. We don't know how many leagues Satan ascended, but his fall was precipitous, dropping him some 60,000 feet instantly, it would seem, and he would have been plummeting still if not for the "ill chance" of being lifted by some 'flatulence' from deep within chaos.
He spreads for flight, and in the surging smoak
Uplifted spurns the ground, thence many a League
As in a cloudy Chair ascending rides [ 930 ]
Audacious, but that seat soon failing, meets
A vast vacuitie: all unawares
Fluttring his pennons vain plumb down he drops
Ten thousand fadom deep, and to this hour
Down had been falling, had not by ill chance [ 935 ]
The strong rebuff of som tumultuous cloud
Instinct with Fire and Nitre hurried him
As many miles aloft: (PL 2.927-938)
Lucky, plucky Satan, who could perhaps supply us with a more accurate depiction of the cosmos and what lies beyond ... if only it were in his interest to do so...