Earth mounds were created by ancient Mesopotamians to be used as temples?

Earth mounds have been found all over the world and nobody has any clue about what they were for. We don't even know who those people were. "Mesopotamians" means "whoever lived between two rivers". The rivers were the Tigris and Euphrates. There is a city there, population about two million, with no evidence of war. The area is not well studied because it is now a war zone.