Situated at the mouth of Arcachon Bay, the Banc d'Arguin is a sandbank that is constantly in flux, shaped by the moods of the Atlantic (it measures around 2km by 2km). Its location opposite the Dune du Pilat means it commands extraordinary views over this mountain of a sand dune. Don't forget your binoculars if you want to spot Sandwich terns and oystercatchers from March to August, and in winter Eurasian curlews, bar-tailed godwits and dunlins.