Inner Seas

The world of Arda was surrounded on all sides by a vast and dark Outer Sea, beneath which the Vala Ulmo dwelt. That Outer Sea was quite different in substance to the seas that ran between the continents of Arda, the Inner Seas. Ulmo placed these Inner Seas under the power of his vassals, the two Maiar of the Sea: Ossë and Uinen.

Greatest of the Inner Seas by far was Belegaer, the Great Sea that divided Aman in the West from Middle-earth in the East. Within Middle-earth there were other lesser seas, three of which we know about in at least some detail: the Seas of Helcar, Núrnen and Rhûn. Early maps of the entirety of Middle-earth suggest that another inland sea existed to the south and east of the familiar northwestern regions. One map¹ shows this as a roughly circular sea named Ringil, while another² makes it much larger - almost an ocean in its own right - and labels it 'East Sea'.