I've recently started work on a historical fantasy setting, and I decided to set it in Mesopotamia, but I'm trying to choose between the empire of Sargon the Great, the time of several empires (the Hittites, Egyptians, Babylonians, and Assyrians), or the Assyrians at the height of their power.
And just a note on the Assyrians, I never realised how massive it was. Seriously, look up the Assyrian Empire in 650 BC.
Their empire stretched from parts of Turkey all the way down to past Thebes in Egypt. Look at the size of that thing!