- Type: Inland Sea.
- Area: 15,430 square miles.
- Elevation: 760 feet.Depth: average. 10 fathoms. deepest point. 46 fathoms. shoals and reefs: many shoals, especially along coasts in the southeastern quarter. Waves and Wind: average wind speed: 6-8 knots.average wave height. 1-2 feet.
- Climate: average annual rainfall 20-35 inches. mean annual temperature 40-50°F average low. Ninui-5°F average high: Urui 75 °F
- Composition: The Gaer Rhunen or Rhûnaer was a shallow inland sea fed by many of the rivers of the plain of Rhovanion. It was large enough to experience tides (which varied about eight inches on average). The influx of several rivers created the illusion of a current which ran counter-clockwise around the Sea. The shoals in the Gaer Rhunen were invisible to inexperienced pilots, and navigation was best left to expert guides. The waters had a faintly salty taste, and despite freezing temperatures in the winter months, the Sea was always free of ice.
Notes: Several tribes of Easterlings derived their sustenance from the Gaer Rhunen. It acted as a highway for much of the trade to the West, and it was also teeming with fish. Few Northmen or Dunedain ever viewed the Sea, but those who had dealings with the Easterlings knew of its importance to their culture.