The characteristics of Mesopotamian civilization included the city-state, irrigation, polytheistic religion, three distinct social classes and the development of the solar calendar. Mesopotamian civilization is thought to have been the first human civilization center of the world.
The Sumerians found the Mesopotamian area before any other group of people and settled there. They built their cities along the Lower Mesopotamia rivers and created technological advances including wheels and plows as well as detailed irrigation systems, using canals and levees, that allowed crops to flourish. In fact, the name "Mesopotamia" means the "land between the rivers."
One of the most important parts of the Mesopotamian civilization was its religion. The Sumerians believed in multiples gods and goddesses, and they built seven cities with a temple at each one dedicated to a different divine figure. Each city also had its own army for protection against other civilizations. Everything that the Sumerians did, they did in consultation with the gods and the goddesses. These deities were instrumental parts of the Sumerians lives.
Another advancement in the Mesopotamian civilization was the invention of the solar calendar. The solar calendar had 12 months that were based around the moon though there were no seasons. It was not until 1582 that the Gregorian calendar was introduced.