 Following the Treaty of Lyon (1601), the Marquisate of Saluzzo, which had defended its independence for more than three centuries, was annexed to the Duchy of Savoy, and therefore the Monte Viso Tunnel lost its strategic importance, seeing alternating occasional openings with long periods of closure.Afterwards, Duke Carlo Emanuele I of Savoy closed the tunnel, in order not to compromise the flow of commercial traffic of the Moncenisio and Monginevro valleys, on which Savoy exercised long-term rights.However, while neighbouring communities continued to value the tunnel for the increased trade that it enabled, it was frequently closed during the following centuries through landslides and rockfalls.