Not to say anything about the NPO, but Rome's greatest achievement was its law. The Greeks, Arabs, and Chinese far surpassed them in science and philosophy. Roman law was their legacy, and the world might be better if Rome had fallen after the end of the republic. The Empire was serf-based, and therefore stagnant, had rampant unemployment, was fed by plunder, and was horribly corrupt, not to mention the general public's huge appetite for violence and slaughter. If the Greeks had stayed as they were, that would have been great, but the Romans? Definitely not. The Greeks had rudimentary steam engines, pistons, pulleys, and even animation - Stuff that wasn't seen for years after the Romans took over.