The southern part of ancient Mesopotamia — the land between the Tigris and Euphrates rivers, in what is now southern Iraq. People lived in cities there from about 3500 BC, and it is usually called the earliest civilisation in the world, or one of the earliest. The people were the Sumerians. Their cities — Ur, Uruk, Eridu, Lagash — were separate small states, each with a temple tower called a ziggurat in the middle. Two things they are famous for. They wrote: cuneiform, wedge-shaped marks pressed into wet clay, is the oldest writing we can read, and because clay does not burn, we still have their tax records, school exercises, and the story of Gilgamesh. And they are believed to have invented the wheel, along with early work on the plough, irrigation canals, and dividing the hour into sixty minutes — that is still their number system, sitting in your watch. In English the word is a name only, used in history and museums; it is not a word you will hear in daily conversation.