Netherworld

The Netherworld has been the imaginary place where ghosts live in since the beginning of The Sims games. Although it hasn't been shown until The Sims 3, it has existed since the series began.

In The Sims 3, once a ghost has become playable the player has the option to return it to its unplayable state by select their tombstone and click "Return to the Netherworld".