The central land of the continent of Aman.

After Melkor's destruction of Almaren, the Valar founded Valinor (the Land of the Valar).
It was part of the lands of Middle-earth until the rebellion of Ar-Pharazôn of Númenor, when Valinor and all the lands in Aman were removed from the visible world.

Since that, only the Elves and selected mortals could reach Valinor by ship from Middle-earth, by following the straight road into the West.
Encyclopedia entry originally written by Annúnagar