New here, dunno if this has been discussed or theorized:

Guillermo Del Toro just did an interview where he states his At the
Mountains of Madness movie is pretty much a bust since it will be the
same plot as Prometheus:

http://www.comicbookmovie.com/fansites/nailbiter111/news/?a=59251



He suggests that Alien and Ridley Scott are heavily influenced by this
story.  I've never read it, but I just read the synopsis on wikipedia. 
It is earily similar to what we know of the plot.



http://en.wikipedia.org/wiki/At_the_Mountains_of_Madness



Plot summary:

The story is written in first-person perspective by the geologist William Dyer, a professor at Miskatonic University.
He writes to disclose hitherto unknown and closely kept secrets in the
hope that he can deter a planned and much publicized scientific
expedition to Antarctica.
On a previous expedition there, a party of scholars from Miskatonic
University, led by Dyer, discovered fantastic and horrific ruins and a
dangerous secret beyond a range of mountains higher than the Himalayas.
The group that discovered and crossed the mountains found the remains
of 14 ancient life forms; completely unknown to science and
unidentifiable as either plants or animals. Six of the specimens are
badly damaged and the others uncannily pristine. Their highly-evolved
features are problematic: their stratum location puts them at a point on the geologic time scale much too early for such features to have naturally evolved yet.

When the main expedition loses contact with this party, Dyer and the
rest of his colleagues travel to their camp to investigate. The camp is
devastated and both the men and the dogs slaughtered, while Gedney
(another member of the sub-expedition) and a dog are missing. Near the
camp they find six star-shaped snow mounds, and one specimen buried
under each. They discover that the better preserved life forms have
vanished, and that some form of dissection
experiment has been done on a deliberately unnamed man and a dog. Dyer
elects to close off the area from which they took their samples.

Dyer and a graduate student named Danforth fly an airplane over the
mountains, which they soon realize are the outer wall of a huge,
abandoned stone city of cubes and cones, utterly alien compared with any
human architecture. Because of their resemblance to creatures of myth mentioned in the Necronomicon, the builders of this lost civilization are dubbed the "Elder Things".
By exploring these fantastic structures, the men are able to learn the
history of the Elder Things by interpreting their magnificent hieroglyphic murals: The Elder Things first came to Earth shortly after the Moon was pulled loose from the planet and were the creators of life. They built their cities with the help of "Shoggoths",
biological entities created to perform any task, assume any form, and
reflect any thought. As more buildings are explored, a fantastic vista
opens of the history of races beyond the scope of man's understanding,
including the Elder Things' conflicts with the Star-spawn of Cthulhu and the Mi-go
who arrived on Earth some time after the Elder Things themselves. The
images also reflect a degradation in the order of this civilization, as
the Shoggoths gain independence. As more resources are applied to
maintaining order, the etchings become haphazard and primitive. The
murals also allude to some unnamed evil in an even larger mountain range
just past their city which even they fear greatly. Eventually, as
Antarctica became uninhabitable even for the Elder Things, they migrated
into a large, subterranean ocean.

The two eventually realize they are not alone in the city. The Elder
Things missing from Lake's camp had somehow returned to life and, after
slaughtering the explorers, returned to the city of their origin. Dyer
and Danforth discover traces of the Elder Things' earlier exploration,
as well as sledges containing the corpses of Gedney and the dog missing
from the camp.

As the two progress further into the city, they are ultimately drawn
to a massive, ominous entrance which is the opening of a tunnel which
they believe leads into the subterranean region described in the murals.
Compulsively they are drawn in, finding further horrors: evidence of
dead Elder Things caught in a brutal struggle and blind six-foot-tall
penguins wandering around placidly, apparently as livestock for the
unknown forms of life which lurked inside the subterranean abyss. They
are then confronted with an immense, ululating horror in the form of a
black, bubbling mass, which after a brief glimpse they identify as a
Shoggoth. Danforth and Dyer escape with their lives using luck and
diversion. On the plane high above the plateau, Danforth looks back and
sees something that causes him to lose his sanity. He refuses to tell
anyone (even Dyer) what he saw, though it is implied that it has
something to do with what lies beyond the larger mountain range that
even the Elder Things feared.

Professor Dyer concludes that the Elder Things and their civilization
were eventually destroyed by the Shoggoths they created and that this
entity has sustained itself on the enormous penguins since eons past. He
begs the planners of the next proposed Antarctic expedition to stay
away from things that should not be loosed on this Earth.