An, whom the Akkadians called Anu, is the sky and the father of the Sumerian gods, the ultimate source of authority. His name is simply the word for heaven, and the cuneiform sign that writes it is also the sign for god (dingir), placed before every divine name, so that the small star-shaped sign standing at the head of every god's name in the script is, in a sense, Anu. He presides over the divine assembly that fixes destinies and confers kingship, the source from which legitimate rule descends to earth. His city is Uruk, where he shared the Eanna temple with Inanna, though she came in time to overshadow him there.
Anu's name appears among the very earliest written signs known, in the archaic administrative tablets from Uruk dated to roughly 3100 BCE, making him, in a real sense, as old as writing itself in Mesopotamia. He is rarely shown in human form in art; instead his presence is marked by the horned cap or tiara that became the generic sign of divinity, worn by every god in Mesopotamian art regardless of rank, a convention usually explained as deriving from Anu's own crown lent, in effect, to the whole pantheon. Excavation of the Eanna precinct at Uruk has uncovered building phases reaching back to the Uruk period in the fourth millennium BCE, one of the longest continuously sacred plots of ground anywhere in the ancient world, even as the temple's dedication shifted over the centuries.