Interestingly, inside the massive wall, I was told, there was a maze which stretched dozens of yards, so even if the marauders breached the outer wall, they would have to negotiate the maze before they could get into the main area.
Most of the really good stuff at Babylon was stolen by the Germans and is now on display in the Pergamon Museum in Berlin.
Here, for example is a photo of the Ishtar Gate - the main entryway to Babylon from the Pergamon Museum's website