Mictlan was the mythological underworld of which ancient civilisation?

The Aztecs were a Mesoamerican culture that flourished in central Mexico in the post-classic period from 1300 to 1521. Mictlan is the underworld of Aztec mythology. Most people who die would travel to Mictlan, although other possibilities exist. Mictlan consisted of nine distinct levels.

The journey from the first level to the ninth is difficult and takes four years, but the dead are aided by the psychopomp (a guide), Xolotl. The dead must pass many challenges, such as crossing a mountain range where the mountains crash into each other, a field with the wind that blows flesh-scraping knives, and a river of blood with fearsome jaguars.

Mictlan also features in the Aztec creation myth. Mictlantecuhtli (the Lord of the Land of the Dead) set a pit to trap Quetzalcoatl (a serpent). When Quetzalcoatl entered Mictlan, Mictlantecuhtli was waiting. He asked Quetzalcoatl to travel around Mictlan four times blowing a conch shell with no holes. Quetzalcoatl eventually put some bees in the conch shell to make a sound. Fooled, Mictlantecuhtli showed Quetzalcoatl to the bones. But Quetzalcoatl fell into the pit and some of the bones broke. The Aztecs believed this is why people's height is different.

Other deities in Mictlan include Cihuacoatl (who commanded Mictlan spirits called Cihuateteo), Acolmiztli, Chalmecacihuilt, Chalmecatl and Acolnahuacatl.