In the Sumerian city, the Ziggurat of Ur was a skyscraper over the city. It was about 20 metres (66 feet) tall. The only level that remains today is the bottom. There were big staircases to get up and down. 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 that were perfect. After drying they took 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. Later the Ziggurat became more than a place for gods. There were workshops for craftworkers. For the priests, there were temples to do worship. 