When Cyrus had made all the mainland submit to him, he attacked the Assyrians. In Assyria there are many other great cities, but the most famous and the strongest was Babylon , where the royal dwelling had been established after the destruction of Ninus . Babylon was a city such as I will now describe. It lies in a great plain, and is in shape a square, each side fifteen miles in length; thus sixty miles make the complete circuit of the city. Such is the size of the city of Babylon ; and it was planned like no other city of which we know. Around it runs first a moat deep and wide and full of water, and then a wall eighty three feet thick and three hundred thirty three feet high. The royal measure is greater by three fingers' breadth than the common measure.