Aman, the lands in the Uttermost West (somewhat conjectural)

A name for the lands in the distant West of the World, beyond the Enchanted Isles and the Shadowy Seas, where lay Aman and Valinor, the land of the Valar. More commonly simply called 'the West', even during the First Age these were difficult regions to reach, because the Valar had filled the seas eastward of their realm with enchantments and shadows. When Men were settled on Númenor the Valar explicitly forbade them from sailing into the Uttermost West - the so-called Ban of the Valar - and it was the breaking of this Ban that led to the Downfall of Númenor. After that time, the lands of Aman were taken out of the world entirely, so that the Uttermost West could never be reached by mortal mariners except by special grace, and was only accessible along the Straight Road open to the Elves.