No one knows the precise reasons why Carsulae was abandoned, but there are four reasons that seem plausible a) that it was destroyed and the site made inhospitable by an earthquake (however, most viable cities hit by earthquakes are rebuilt), b) that it lost its importance and becomes increasingly impoverished because most of the north-south traffic used East branch of the Via Flaminia (Terni, Spoleto, Foligno), c) Carsuale was built in a valley without defensive walls, in the early Middle Ages people tend to move to better defended settlements due to the political instability that sets in. J.B. Ward-Perkins suggested another effect of increasingly unsettled third century, when the very trunk roads that had been economic lifelines became access roads for hordes of marauders: "Henceforth the tendency must have been to move away from the roads, until by the Middle Ages the roads themselves were as bare of settlement as they had been when they were first built.", d) In the 6th - 8th Century during the period of the "Longobard Corridor" the Western branch of the Via Flaminia is blocked by a conflictual border between the Imperial Territory and the Duchy of Spoleto, In this period most North-South traffic moves to the West along the Via Amerina.