Tall ships and tall kings
Three times three,
What brought they from the foundered land
Over the flowing sea?
Seven stars and seven stones
And one white tree.
Númenor was an enormous island west of Beleriand and Middle Earth, and home to the greatest realm of men (reward for their part in defeating Morgoth). 
 However, in their power the Númenóreans grew haughty and vain, until the last and most powerful of their kings, Ar-Pharazôn, defeated Sauron and took him hostage, giving him opportunity to corrupt the ruling caste of Númenóreans, and convincing them to worship Morgoth and “assault” the Blessed Realm of the Valar – this led to the destruction of Númenor (think Atlantis). Hence, Númenor is a “foundered land.” 
 A few of the uncorrupted, who remained friends of elves and worshippers of the Valar, fled to Middle Earth – they were led by Elendil and his son Isildur. 
 The Númenóreans were known for their exceptional height and longevity of age.