France built the defensive barrier along the German and Italian borders during the interwar period. The structures built to seal passing points and main roads were formed by underground blocks. The soldiers could live here self-sufficiently for months, just like in a submarine. The “Alpes Maritimes Fortified Sector” runs from Col de la Bonnette to the Mediterranean via the Tinée Valley, Vésubie Valley, outside Sospel and ends near Menton at the foot of Cap Martin.
