A lake that lay in the central regions of Middle-earth in very ancient times, when the world was illuminated by the Lamps of the Valar. The Great Lake was halfway between the two Lamps, Illuin in the north and Ormal in the south, and was bathed in their mingled lights. Within the Great Lake was an island, Almaren, on which was the first dwelling of the Valar in Arda.

While the Valar dwelt in peace on Almaren, Melkor secretly re-entered the world and brought down both of the Lamps of the Valar. In their fall they wrought destruction across the world, and Almaren was lost. The chaos was so great that the Great Lake apparently ceased to exist; though its fate is not specifically explained, we have no reference to it after this event.