Also called: Halls of Waiting, House of Dead. The word “Mandos” comes from two words: "prison" and "fortress".

The Halls of Mandos were the dwellings of Námo of the Valar, who was also called Mandos. They were located on the deserted western shore of the Undying Lands- facing the Encircling Sea and the Walls of Night.

They were said to grow in size as the World advanced, and the walls were hung with the tapestries of Vairë, Mandos’s wife. The tapestries depicted all the events of the world's unfolding history.

It was to the Halls of Mandos that the spirits of Elves and Men were gathered to await their different fates, and so were the Halls also called the Halls of Waiting. After a time, the near-immortal Elves could be re-embodied, and return from the Halls to their kin in Aman. Men had a different fate, one which only Ilúvatar, Mandos and Manwë truly understood.

**Some additional information provided by Gil_Estel101**
Encyclopedia entry originally written by Abraon