Sumeria, the earliest known city civilization, set the religious tone for the rest of Mesopotamia. Sumeria seemed to be saturated with divine presence and its concept of myriad gods and goddesses, each controlling their own aspect of life, together with the sacrifices required to humor them, greatly influenced other Mesopotamian religions.

3300 BC
- Immigrants from Anatolia arrive in Sumeria and build city-states
3100 BC
- Temples built at Uruk, along the ancient course of the Euphrates
2600 BC
- Sumerian king list (a list of the names of Sumerian kings, discovered by archeologists)
2200 BC
- Ziggurats built in Sumeria
2000 BC
- Myths of Gilgamesh, King of Uruk, written in the Sumerian language on clay tablets
1720 BC
- Shift in the position of the Euphrates River leads to collapse of Nippur and other Sumerian cities
GODS AND GHOSTS
The vast Sumerian pantheon represented aspects of the world – the harvest, the wind or the sun – in divine form. The principal deity was Anu, ruler of Heaven, who was later replaced by Enlil, Lord of the Winds. There were also some 3,000 other deities in Sumeria. In addition, individual villages had their own local gods, as did inanimate objects. Enlil, for instance, was the god of the hoe through his connection with the moist spring wind and the planting season. Enlil’s son, Ninurta, was the god of the plough. Concepts of reincarnation and the afterlife were alien to Sumerian theology. The dead, Sumerians believed, had no specific place in which to continue in the same style they had known while living. Consequently, the living were thought to be constantly at risk from their presence, and only by regular offerings of food and drink could these ghosts be dissuaded from haunting them.
The Epic of Gilgamesh
Gilgamesh, the fifth king of the first dynasty of Uruk, in present-day southern Iraq, reigned in around 2600 BC and was the subject of five Sumerian poems probably written six centuries later. Gilgamesh became the hero not only of Sumerian but also of Hittite, Akkadian and Assyrian legend. The Epic tells how Gilgamesh searches for immortality, but after many adventures, he fails and is forced to recognize the reality of death.
THE PRIESTS
Priests in the Sumerian temples acted as conduits between the gods and human beings. They conducted the daily services and presided over festivals, such as Akitu, the festival of the new year, which fell approximately at the time of the Spring equinox. They interpreted the entrails of sacrificed animals, usually sheep, in order to learn the divine will. They performed public sacrifices which usually consisted of goats, cattle, and birds, as well as sheep. The divine portion of an animal sacrifice comprised the right leg, the kidneys, and a piece of meat for roasting. The rest of the animal sacrifices were consumed at the temple feast. In addition, libations of water were poured over sheaves of grain or bunches of dates so that the gods of fertility would grant the rain for healthy crops. All manner of offerings were brought to the priests in the temples for use by the gods: clothing, beds, chairs, drinking vessels, jewels, ornaments, or weapons. All these were classed as divine property and were placed in the temple treasuries. Clothing was first offered to the gods, then distributed among the priests and other officials who staffed the temples. The high priest had first pick, and the last went to the lowly sweepers of the temple courtyards.
ZIGGURATS
The high temple towers known as ziggurats, which were topped by a small temple dedicated to one of the Mesopotamian deities, were a feature of religious architecture around 2200 BC and 500 BC. The practice of building ziggurats began in Sumeria, spreading later to Babylonia and Assyria. The step-sided ziggurat bore little resemblance to the later pyramids of Ancient Egypt. There were no internal rooms or passageways and the core was made of mud brick, with baked brick covering the exterior. The shape was either square or rectangular, with measurements averaging 40 or 50 sq m (130 or 165 sq ft) at the base. The most complete extant ziggurat, now named Tall al-Muqayyar, was built at Ur in southwest Sumeria (present-day southern Iraq). The most famous was the Tower of Babel, which is popularly believed to have had links with the ziggurat at the temple of Marduk, the national god of Babylonia. The Tower of Babel, having been built in the vicinity of Babylon, is regarded by some archaeologists and anthropologists as an extension of the worship of Marduk at his ziggurat temple in the city.