Around 3500 BC, towns, temples, palaces and scripts appeared here, becoming one of the earliest cradles of civilization.
From about 3500 BC, cities with walls appeared in Sumer area of the two river basins.
City of ur stands on the east bank of the Euphrates River, surrounded by brick walls, and there is a wide moat outside the wall, which is convenient for traffic and strengthens the defense capability. There are many merchant ships moored by the river, which transport goods from one settlement to another.
The narrow streets in the city crisscross, and the streets are paved with dry bricks. The streets are lined with houses, shops and public facilities, and the king's spacious palace is also here. On the earthen platform in the center of the city, there is a temple dedicated to the moon god.
There are some villages and towns around the city, and most of the cultivated land belongs to temples. Farmers must hand over some grain they have harvested to the temple. Sumerians lacked stones, metals and hardwoods, all of which had to be imported from other places. In exchange, Sumerians sold the grain, wool, jars and metal products they produced.
In the long history of thousands of years, Sumerians first settled in the lower reaches of the two river basins and established many small countries. In the 8th century BC/KLOC-0, King Hammurabi of Babylon unified the two river basins and established a powerful country with Babylon as its capital.
Sumerians invented hieroglyphics. They used reeds and bone sticks with triangular tips as pens to write on wet clay tablets. Characters carved on clay tablets are called "cuneiform characters" because their strokes are like wedges. This kind of writing is widely circulated in West Asia.
People in the two river basins compiled the lunar calendar by observing the laws of the moon's profit and loss.