§ Of Eldamar and the Princes of the Eldalië The Silmarillion

In time the hosts of the Vanyar and the Noldor came to the last western shores of the Hither Lands. In the north these shores, in the ancient days after the Battle of the Powers, bent ever westward, until in the northernmost parts of Arda only a narrow sea divided Aman, upon which Valinor was built, from the Hither Lands; but this narrow sea was filled with grinding ice, because of the violence of the frosts of Melkor. Therefore Oromë did not lead the hosts of the Eldalië into the far north, but brought them to the fair lands about the River Sirion, that afterwards were named Beleriand; and from those shores whence first the Eldar looked in fear and wonder on the Sea there stretched an ocean, wide and dark and deep, between them and the Mountains of Aman.