This colossal sand dune (sometimes referred to as the Dune de Pyla because of its location 4km from the small seaside resort town of Pyla-sur-Mer), 8km south of Arcachon, stretches from the mouth of the Bassin d'Arcachon southwards for 2.7km. Already Europe's largest, the dune is growing eastwards 1.5m a year – it has swallowed trees, a road junction and even a hotel, so local lore claims. The view from the top – approximately 115m above sea level – is magnificent.
To the west you see the sandy shoals at the mouth of the Bassin d'Arcachon, including Cap Ferret and the Banc d'Arguin bird reserve, where up to 6000 couples of Sandwich terns nest each spring. Dense dark-green forests of maritime pines, oaks, ferns and strawberry trees (whose wood is traditionally used to build oyster-farmer shacks) stretch from the base of the dune eastwards almost as far as the eye can see.
Between Easter and early to mid-November, a wooden staircase – between 150 and 160 steps depending on the year – is erected on one side of the dune to help tourists scramble to its sandy top. Otherwise, clamber exhaustedly up the steep sand mountain – and exercise your inner child by flying down at an exhilarating sprint if you dare. Bare foot is preferable, although the sand can be perishingly cold in winter and as hot as burning coals in the height of summer.
Be warned that it can be desperately windy atop the dune: swirling, whip-lashing sand can be particularly unpleasant for younger children. Take care swimming in this area: powerful currents swirl out to sea from deceptively tranquil little bays.