Record: 6.50 km
The Caronte canal or Caronte channel is a canal that links the Étang de Berre to the Mediterranean Sea (Gulf of Fos), in the Bouches-du-Rhône.
It is 6.5 kilometres long and 250 metres wide. Its depth is currently 10 metres.
The Lagoon of Berre closed around 7000 BC: following the Flandrian transgression, the plain filled up through a valley of erosion incising the limestone massif. This passage is filled in by the accumulation of sediments, isolating the pond from the Mediterranean Sea1.
It was during the Roman period that the Caronte Canal was built.
The canal crosses the town of Martigues, cutting out an island lined with quays that give the town an air of "Venice of Provence". On one of the arms of the canal, in the middle of the town of Martigues, a lift bridge was built to allow the passage of boats over one metre high, and in particular the oil tankers that serve the refineries of La Mède and Berre.
The railway line from Marseille to Miramas via Port-de-Bouc crosses the canal on a metal viaduct built in 1915. Almost one kilometre long, it overhangs the canal at almost 25 m above the water level. As this height does not allow the passage of large ships, the central part of the viaduct was mounted on a pivoting axis, which allows the railway line to be removed to allow out-of-gauge maritime traffic to pass. The Caronte viaduct is an exceptional example of railway architecture.