This 2.5m-high dyke was built in the 19th century to cut the delta off from the sea, making the southern Camargue arable. A 20km-long walking and cycling track runs along its length, linking Stes-Maries with the solar-powered Phare de la Gacholle (1882), a lighthouse automated in the 1960s. Footpaths cut down to lovely sandy beaches and views of pink flamingos strutting across the marshy planes are second to none. Walking on the fragile sand dunes is forbidden, as is driving.