The world's earliest civilization, dated
about 3500 BC, and located at the confluence
of the Tigris and Euphrates rivers in lower
Mesopotamia (present-day Iraq). It was a
city-state with priests as secular rulers.
Sumerian culture was based on the taxation of
the surplus produced by agricultural
villagers to support the urban ruling class
and its public-works programme, which
included state-controlled irrigation. Cities
included Lagash, Eridu, and Ur.