"At the Mountains of Madness" was a story written by H. P. Lovecraft and published between February and April 1936 in Astounding Stories. It dealt with "the Old One a.k.a. the Elder Thing".

Twelve million years before the 20th century, a Celestis fictional generator used the novella to bring the Elder Things and their city into existence in Antarctica. (PROSE: The Taking of Planet 5)