The Sumerians widely regarded their divinities as responsible for all matters pertaining to the natural and social orders of their society.
Later, this role was supplanted by kings, but priests continued to exert great influence on Sumerian society.
In early times, Sumerian temples were simple, one-room structures, sometimes built on elevated platforms.
First, Nammu, the primeval waters, gave birth to Ki (the earth) and An (the sky), who mated together and produced a son named Enlil.
Heaven was reserved exclusively for deities and, upon their deaths, all mortals' spirits, regardless of their behavior while alive, were believed to go to Kur, a cold, dark cavern deep beneath the earth, which was ruled by the goddess Ereshkigal and where the only food available was dry dust.
During the Akkadian Empire, Inanna, the goddess of sex, beauty, and warfare, was widely venerated across Sumer and appeared in many myths, including the famous story of her descent into the Underworld.
Scholars of comparative mythology have noticed parallels between the stories of the ancient Sumerians and those recorded later in the early parts of the Hebrew Bible.
Toward the end of the Sumerian civilization, ziggurats became the preferred temple structure for Mesopotamian religious centers.
Until the advent of the Lugal ("King"), Sumerian city-states were under a virtually theocratic government controlled by various En or Ensí, who served as the high priests of the cults of the city gods.
Priests were responsible for continuing the cultural and religious traditions of their city-state, and were viewed as mediators between humans and the cosmic and terrestrial forces.
The priesthood resided full-time in temple complexes, and administered matters of state including the large irrigation processes necessary for the civilization's survival.
[10] During the Third Dynasty of Ur, the Sumerian city-state of Lagash was said to have had sixty-two "lamentation priests" who were accompanied by 180 vocalists and instrumentalists.
[12] Underneath the terrestrial earth, which formed the base of the dome, existed an underworld and a freshwater ocean called the Abzu.
[15]: 37–41 The ancient Mesopotamians regarded the sky as a series of domes (usually three, but sometimes seven) covering the flat earth[16]: 180 and a place where holy stars resided.
[21] Instead, after a person died, his or her soul went to Kur (later known as Irkalla), a dark shadowy underworld, located deep below the surface of the earth.
[21][22] The Sumerian afterlife was a dark, dreary cavern located deep below the ground,[22][23] where inhabitants were believed to continue "a shadowy version of life on earth".
[20]: 58 Nonetheless, there are assumptions according to which treasures in wealthy graves had been intended as offerings for Utu and the Anunnaki, so that the deceased would receive special favors in the underworld.
[20]: 134 [16]: 184 Galla were a class of demons that were believed to reside in the underworld;[20]: 85 their primary purpose appears to have been to drag unfortunate mortals back to Kur.
[24] The Sumerians originally practiced a polytheistic religion, with anthropomorphic deities representing cosmic and terrestrial forces in their world.
[16]: 178–179 The earliest Sumerian literature of the third millennium BC identifies four primary deities: An, Enlil, Ninhursag, and Enki.
These early deities were believed to occasionally behave mischievously towards each other, but were generally viewed as being involved in co-operative creative ordering.
[29]: 58 [30]: 231–234 His primary consort was Ninlil, the goddess of the south wind,[31]: 106 who was one of the patron deities of Nippur and was believed to reside in the same temple as Enlil.
[16]: 184 Nammu was a goddess representing the primeval waters (Engur), who gave birth to An (heaven) and Ki (earth) and the first deities; while she is rarely attested as an object of cult, she likely played a central role in the early cosmogony of Eridu, and in later periods continued to appear in texts related to exorcisms.
[43] The Sumerians had a linguistic and cultural exchange with the Semitic Akkadian peoples in northern Mesopotamia for generations prior to the usurpation of their territories by Sargon of Akkad in 2340 BC.
Sumerian mythology and religious practices were rapidly integrated into Akkadian culture,[44] The Amorite Babylonians gained dominance over southern Mesopotamia by the mid-17th century BC.