Cosmology
The universe first appeared when Nammu, a presumably formless abyss, curled in upon herself, and in an act of self-procreation gave birth to An, god of heaven and Ki, goddess of Earth (commonly referred to as Ninhursag).
The union of An and Ki produced Enlil, lord of wind, who eventually became leader of the pantheon. After the banishment of Enlil from Dilmun (the home of the gods) for raping Ninlil, Ninlil has a child, Sin (god of the moon), also known as Nanna. Sin and Ningal gave birth to Inanna (goddess of love and war) and to Utu/Shamash (god of the sun). During Enlil's banishment, he fathered three underworld deities with Ninlil, most notably Nergal.
Nammu also gave birth to Enki, god of the watery abyss, or the Abzu. Enki also controlled the Me, holy decrees that governed such basic things as physics and complex things such as social order and law.
This accounts for the origin of most of the world as we know it.
Sources
The earliest known writings on the Sumerian cosmology stem from Enheduanna.
see also mythology, Norse mythology