The Halls of Mandos hold the souls of the dead and are the dwelling place of Mandos.
The dwellings of the Doomsman of the Valar, the mighty Vala called Námo (Mandos), though he was more often given the name Mandos after his own halls. The name comes from two Elvish words meaning 'prison' and 'fortress', and the Halls stood on the western shores of Valinor, looking out across the Encircling Sea. They were said to grow in size as the World aged, and their walls were hung with the tapestries of Námo's spouse Vairë, depicting all the events of 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 Mandos was given its common name of the Halls of Waiting. The Elves, after a period of cleansing and self-reflection, could be reincarnated into bodies identical to those of their prior life; however those elves who had offended the Valar or committed particularly heinous misdeeds were doomed to wait in the halls until the end of time. Men go to a different hall to be judged by Mandos before leaving Arda. Men had a different fate, a fate which not even Manwë truly understood."