Which of these was a type of ancient Mesopotamian massive structure with receding levels?

Hello all, it's about time someone entered a comment to this question, no matter how insignificant the comment really is. I mean people enter comment after comment on most questions without really thinking. Guess that's all I have to say about this today. I mean really I'll catch ya all later on the flipside...whatever that means. Live long and prosper...everyone should voice their comments to have another Star Trek movie made.