The Canal de Marseille au Rhône connects the Mediterranean Sea at Marseille to the Rhône at Arles. The section between Marignane and Marseille has been closed since the collapse of the Rove Tunnel in 1963.
Wikipedia https://en.wikipedia.org/wiki/Canal_de_Marseille_au_Rhône
Coordinates 43°24'11.573" N 5°10'21.581" E
