Ziggurats.
The mesopotamia region was famous for Ziggurats. Some of the most famous Ziggurats of this region are known as The Great Ziggurat of Ur and Khorasabad. These structures looked like gigantic pyramids and had the form of hundreds of steps. They were not considered places of worship. Instead they were merely believed to house gods. That is the reason why sacrifices were made here and offerings to appease the god were made here too. This was a tradition that went on during the 3rd millennium BC.