Neither Babylon nor Assyria were established as greats until the 2nd mill. BCE (doing a Ph.D. on partly that subject now) with Hammurabi and his immediate predecessors in 1800s-1700s BCE and the Assyrian trading network at the approx. same time, so I would go for Egypt or China there. In fact, the Assyrian empire itself is late 2nd mill., into 1st mill. BCE. Of course, the Sumerian culture would have trumped these.