Ur had three levels. The richer, like government officials priests and soldiers were at the top. The second level was for merchants, teachers, laborers, farmers and craftmakers. The bottom was for slaves captured in battle. Burials at Ur give insight into people's social standing. Kings and queens were buried with treasure. Wealthy people were buried with less.
Since irrigation gave Ur abundant crops, not everybody needed to work on farms. People learned other skills. Sir Leonard Wooly made a tablet that listed Ur's special workers. The chisel workers made sculptures; the gem cutters made gems, and the fuller stomped on woven wool to make them soft. The metal workers made weapons. Cities have different groups. Some of the richer people are more powerful.
In the Sumerian City, the ziggurats stood like modern skyscrapers over the city. Some ziggurats stood 70 feet tall. Later the ziggurats became more than a place for gods. There were workshops for craftworkers. For the priests, they were temples to do worship. There were big staircases to get up and down.
The only level that remains today is the bottom. They tell a lot about the people who built them. Sumerians had no tools and machinery like us. They were careful brick builders. Brickmakers formed mud bricks there were perfect. After drying they take them to the site and set them in place with bitumen. Bitumen is a thick sticky black stuff. It's like asphalt, the stuff they use to pave roads. They braided reeds so they would be stronger, and hooked them up like steel cables.