The ideas is great indeed. And you are right, the author did not make any effort to steer the AI towards a better outcome. For example, the "great river" is Danube, it obviously exists today, and it is way larger than what AI has generated. This takes away from the immense scale of the Roman achievement. Trajan's Bridge over the Danube [1] was by far the largest bridge constructed by that time (fun fact: it was surpassed by another Roman bridge built during Constantine).

[1] https://en.wikipedia.org/wiki/Trajan%27s_Bridge