I was thinking earlier about the elevator connecting Earthen Peak to the Iron Keep, about how nonsensical it is. Well, I think I understand it now.
In the introduction of Dark Souls II our main character falls down into a whirlpool and wakes on a dry bit of land in (essentially) Ash Lake. Eventually our character wanders out into Majula through a rocky crevice, but he doesn't move up very much on his way out, it is a very gradual incline. Thinking on these things, I have come to theorize that the whole of Dark Souls II may take place at roughly the elevation level of Ash Lake, with one exception, the Iron Keep. I believe the Iron Keep rests upon the surface of the Earth that is supported by the many outstretched branches of the Ash trees; whereas the Earthen Peak, and everything else, reside below the great branches of the Ash trees.
As for the elevator shaft itself, it is in plain sight but we just can't see it due to magic. It is obscured by illusion, the same kind of power responsible for the surface Earth's illusory sun, which was formed by Gwyndolin and tethered to the presence of Gwynevere. I do not believe, however, that Gwyndolin is responsible for this underworld sun & sky; I believe the one responsible to be the Nameless King. He likely possesses the same sun-like illusory power as Gwyndolin. The Nameless King, or Faraam (as he is named in Dark Souls II), left Anor Londo to form his own kingdom, and his faithful followed him, some of whom likely built the kingdom of Drangleic (a land dedicated to dragons) and its surrounding lands (such as Forossa). The Nameless King, being a sun god, would welcome its sight, even if it is illusory, and would establish its presence for the people as well (similar in some respects to Gwyndolin, though I think Gwyndolin did it more for control rather than the magnanimity shown by the Nameless King).
These illusory powers would also explain the sky at Archdragon Peak in Dark Souls III. In Dark Souls III once the sun becomes black and ringed with red, as if it's bleeding towards the Earth, the sun takes on that appearance everywhere, except at Archdragon Peak.
Thoughts?