The Nahuatl or Aztec underworld. According to Aztec legend, there were nine levels of the Mictlan. Quetzalcoatl accompanied by Xolotl had to descend there to find the bones of humanity. See: Klipoth and Xibalba.
“Gnosis is lived upon facts, withers away in abstractions, and is difficult to find even in the noblest of thoughts.”