One of the three things that made Mesopotamia advanced is that they were the first to make cities. The cities had houses, villagers, farmers, slaves, traders, men, women, and children. The cities also had canals with water and they grew plants by them. The cities were very organized and had a lot of things they needed.
The second thing that proved they were advanced was Hammurabi's code. It was the first set of laws written. Hammurabi made all the codes and everyone had to follow them. There were 282 laws. A few of the laws are different for different people. For example, if a rich guy poked a slaves eye out, he would have to pay the slaves owner the slaves value, but if a poor man poked a slaves eye out, his eye would be poked out too.
The last thing that proved they were advanced was they had priest and a giant temple like thing where they worshiped many gods, also known as polytheism. Almost everyone worshiped many gods, some worshiped none or one.