Mesopotamia Plain is an extremely fertile land located in the lower reaches of Euphrates River and Tigris River, also known as the crescent zone. In 5000 BC, a dark-skinned race from northwest India came to settle here. This is Sumerian. They are agricultural tribes who have mastered certain labor skills and know how to cast iron. The fertile land in Mesopotamia helped them to develop agriculture to a higher level, so the exchange of surplus agricultural products gradually developed. Their building capacity is constantly improving, from two or three mud brick huts to larger buildings made of natural stones obtained through exchange. They also invented the pottery turntable, thus making all kinds of utensils, such as bowls, plates, cups, cans and so on. They weave boats with reeds, covered with hides and gum, which enables them to go from one bank of the river to the other. The invention of this kind of vehicle is a milestone. It is this kind of boat that broke the closed state between various regions for the first time and gradually led to the emergence of big cities.