I want to put a plug in for a book that I ordered for our library when I was doing my “Creation in Ancient Mesopotamia” series last spring, but I have just had a chance to look at it now that classes are finished. The book is Wayne Horowitz, Mesopotamian Cosmic Geography (Eisenbrauns, 1998; Buy from Amazon.ca or Amazon.com or Eisenbrauns).
This is an excellent discussion of the ancient texts that relate to how the Mesopotamians viewed the cosmos. It discusses a number of different Sumerian and Akkadian sources for Mesopotamian cosmic geography, including the Mappi Mundi, the Sargon Geography, Gilgamesh, Enuma Elish, among others. Then he surveys the different regions of the universe according to Mesopotamian thought.
All in all this is a great resource, though it ends somewhat abruptly. It would have been great to have a concluding chapter that synthesizes his findings and even to relate it to the Israelite conception of cosmic geography for us biblical scholars.