Nippur, located in the heart of the Tigris-Euphrates floodplain, was one of the most important cities of ancient Mesopotamia. It was occupied as early as the Hajji Muhammad phase of the Ubaid period (circa 5000 B.C.). It lay on a branch of the Euphrates, nearly equidistant between Sippar in the north and Ur in the south; in effect, on the border between Sumer and Akkad. Nippur also served as the major religious center of Mesopotamia, being the site of the Ekur, temple of Enlil, who was the paramount deity of the Sumerian pantheon.

Probably because of its geographically strategic position and religious character, there is no trace in Mesopotamian historical tradition of any king or dynasty that was centered on Nippur ever holding political dominance. But nearly all of the kings of Sumer and Akkad did seek legitimacy for their rule through recognition there. The city was large, by the end of the 3rd millennium B.C., covering some 135–150 hectares within its walls. And it was prosperous, being the object of continuous royal/state investments in the form of construction projects such as its fortification wall and temple buildings, with the temples constantly attracting pious donations.

In the late 18th century B.C., however, it seems that Nippur's fortunes began to fluctuate. Due perhaps to a combination of politico-economic and environmental factors, including drought and the instability of the branch of the Euphrates on which it was located, Nippur experienced periodic "abandonments" and resurgences due to, or accompanied by royal/state investments. The archaeological and written evidence suggests, for example, that the city was largely "abandoned" for three hundred years from the late 18th through the end of the 15th century B. C., but revitalized under the Kassite kings in the 14th and 13th centuries. So too, Nippur appears to have been largely "abandoned" in the first century and a half of the Parthian era (i.e., the last 150 years B.C.), but re-invigorated by Vologases II (A.D. 77–80), as part of a deliberate strategy to control international trade by curbing the expansionist policies of Characene.

The ruins of ancient Nippur lie in southern Iraq, just north of modern Afak, and about 180 km southwest of Baghdad. The site stands nearly 20 meters above the immediately surrounding plain, and measures more than a kilometer and a half across, northeast to southwest. The mound is divided into an eastern and a western portion by the dried bed of a canal. The southern tip of the eastern mound, known as Tablet Hill or the Scribal Quarter–large numbers of tablets were found there in the 19th century–is separated by a shallow gully from the northern part, which is usually called the Religious Quarter because of the temples located there. The remains of the city's fortification wall are marked by chains of low mounds on the far northeast and southwest of the site.

Comprehensive information on Nippur’s various stages of occupation and its religious significance can be found in the following websites and their associated bibliographies:

Nippur: Sacred City of Enlil, Supreme God of Sumer and Akkad 

Patterns of Occupation at Nippur