The Mercantour is the mountainous area bordering France and Italy where the Alps come down to the Mediterranean sea. The wall of Alps of at least 2500 m. altitude presents a natural frontier that has been disputed over many centuries.
We visited Sospel, with a quaint bridge over the river which includes a fortified gatehouse that was formerly a frontier post. Nearby Castillon was a post on the Alpine section of the Maginot Line.
Further back in to France, St. Martin Vésubie heads the valley of the river Vésubie which reaches the river Var by means of a deep and impressive gorge, one of the belvédères of which is intriguingly named "Le Saut des Français".