The Milky Way Sea was located in the middle of the lands of South Heaven, splitting everything into two continents, one comprised of the Eastern Lands and the Northern Reaches, the other of the Southern Domain and the Western Desert.
The area taken up by the Milky Way Sea is huge, far greater than either of the two continents. If you compared it in size with the Southern Domain, the Milky Way Sea would be approximately five times as large.
Therefore, it was divided up into four sections called Rings. The part outside of the Four Rings was called the Outer Sea.
The boundless sea was constantly plagued with hurricanes that swept about, causing huge waves to spring up. Still, there were many islands to be found, some large, some small, which meant that there were Cultivators too.