J.R.R. Tolkien placed the fictional island kingdom of Númenor between Middle-earth and Aman.
Númenor was created by the Valar after the War of Wrath as a reward for the Men who had supported the Elves during the First Age. Its people, the Númenóreans, were granted a longer lifespan and a prosperous island home in the western sea.
The island’s history is one of gradual decline. Númenóreans became increasingly concerned with death and eventually challenged the Ban of the Valar, which prohibited them from sailing to Aman. Under King Ar-Pharazôn, a great armada attacked the Undying Lands.
As punishment, Númenor was destroyed and reshaped in the Downfall. Elendil and his sons escaped and later founded the kingdoms of Arnor and Gondor in Middle-earth. The island’s destruction is described in Tolkien’s mythology as a major turning point in the history of Men.