Netherworld

The place to which one's spirit descends upon death, conceived as below the surface of the earth.

"In some religions, one's soul departs to a netherworld, hell, instead of the heavens."

The locale of the spirit world or afterlife, whether deemed to be situated below the world of the living or not.

"While I was astrally projecting, I felt my soul pass through many insubstantial netherworlds."

Specifically, a location of punishment in the afterlife; a hell.

"The missionary was motivated by a sincere desire to rescue souls from eternal torment in the netherworld."

(by extension) A hidden, shadowy, or sinister subculture, such as that of organized crime.

"Richard had been initiated into the netherworld of dog racing by his father, and knew all the popular greyhound performance-enhancing drugs."