The Ziggurat is considered a precursor to the Pyramid. Many early civilizations started to build them at about the same time. Among these are the Sumerians, who were the first, and the Mayans. Ziggurats also appear in a few areas in south eastern Asia. A question among historians is where the original idea came from and whether or not these civilizations on opposite sides of the world were inspired by one another somehow.
The Ziggurat of Ur was one of the first major religious monuments in history, and is one of the major characteristics that makes the Sumerian culture the first civilization.
The city of Ur was the most powerful city among the four major Sumerian cities. Although the Sumerian cities were all of the same civilization, worshiped the same gods, and were all of the same race, they warred over the territory between their cities. Ur's Ziggurat would have been a show of militaristic power just as much as a homage to the gods. It can be noted that the Ziggurat looks like a fortress, and is built in a way that it could be very defensible if needed.
Religion became a major part of Sumerian life, as it did with many early civilizations. The Sumerian Ziggurat was supposed to be a dwelling for one or perhaps multiple gods. It also doubled as a place of worship for zealous civilians of Ur to go and pray.
It's made out of hand-made clay bricks that were sun dried by the Sumerians. These bricks were then assembled into the massive temple that is the Ziggurat. After several layers of brick, the interior of the Ziggurat is filled with sand, as if to prevent anyone from inhabiting the interior of this massive building. Atop the Ziggurat is a temple which would house a Sumerian holy man.
When the Ziggurat was made, it was by far the largest building ever made by man. And it was not devoted to a man, but to the gods. It shows that the Sumerians had an immense amount of respect for their gods in order to spend their time and wealth to construct such a massive structure. However, at the same time, it shows that the Sumerians feared their gods. What did they fear might happen if the Ziggurat was not built?
The Ziggurat's lifetime of use by the Sumerians was relatively short in comparison to the actual existence of the Sumerians. Some time after the Ziggurat was completed, the Elamites conquered the Sumerians and destroyed them city by city. No one knows quite where the Elamites came from. History only accounts that they came from the east and settled in Sumerian land after defeating them. Later they would fight the hardened warrior culture of the Assyrians in vain.