M. Dune du Pilat

The largest sand dune in Europe lies south of Arcachon on the Atlantic. It's about 3 km long and more than 100 meters high. The La Foret campground we stayed in lies at its base, and because the dune is growing at a rate of 4.5 meters per year, the campground may not be around much longer (the Lonely Planet guide says it has already swallowed trees, a road junction, and a hotel).