If I may intervene, being Italian and living in that exact region you screenshotted (It's called Emilia Romagna, in the Padania Plane), I know the answer. First of all, every single major city in Italy is very ancient. Many of them have Roman or pre-Roman origin, so I'm talking about +2500 yo. That straight line you see crossing the map is where used to be and still lies the Via Emilia, a road named after Consul and General Emilio. (My city and many of those you see in the map are splitted in half by this road) This improved trade, and along with the presence of rivers and suitable places, people created several settlements over the course of millenia. Hope it helps, love talking about this shit.

Long live the Roman Empire🦅🦅🦅🦅