In J. R. R. Tolkien's legendarium, Arda is the name given to the Earth in a period of prehistory, wherein the places mentioned in The Lord of the Rings and related material once existed. It included several seas and oceans, and the continents of Middle-earth, the Dark Lands, Aman (The Undying Lands), the island of Númenor, and other lands left largely unnamed by Tolkien.