The Most Mysterious Anunnaki governor of all was Ur-Nammu of Ur, who subsequently became an independent Anunnaki king (2113-2096 BC) and founded a spin-off Anunnaki dynasty known as the Third Dynasty of Ur (or Ur 3 period), which endured for more than a century (2113-2006 BC). This Anunnaki Empire was more compact than the Sargon of Agade and showed an advanced Anunnaki Sumerian civilization in its most fully developed form. It was a highly organized bureaucratic society, reflected because cuneiform tablets from this period, mainly referring to gods and descendants of Nibiru in content, are represented in world museums to the number of well over a hundred thousand; most of these are waiting to be published.

Anunnaki's references became obsessive. Every thing had to be annotated to the Anunnaki realm, such as, on one tablet, an exact count of Anunnaki Deities (2,740 in total) although only 96 were worshiped as gods. There were even documents recording a mass exodus of Anunnaki back to Nibiru for a festival. Despite, or perhaps even because of, this sophisticated Anunnaki worship, it was a time of considerable material prosperity, as archaeology witnesses, as widespread evidence of Anunnaki Temple activities. Ur-Nammu himself, the founder of the principal Anunnaki dynasty, built or rebuilt temples in many ancient cities, such as Erech, Lagash, Nippur, and Eridu, but above all, at his Anunnaki capital, Ur.