"The Great Dune of Pyla is a rare geological phenomenon and a very popular tourist attraction, being the tallest sand dune in Europe...More details (and additional photos) at Unbelievable Info. Discussed at Reddit.
Perhaps many will be surprised to find out that the dune is quite recent, being formed between the 17th and the 19th century, the sand from several other dunes being blown in this location by the strong winds coming from the Atlantic. The entire phenomenon was generated by the sand in the Arcachon Gulf and by the migration of the southern canal, which produced a severe erosion of the eastern shore. Based on historical evidence, between 1826 and 1922 the entire coast around the Pyla dune has been eroded by 1,650 feet and all the plants and trees covering the western side of the La Grave dune has been destroyed. Without any plants to hold the soil in place, the sands were moved by the wind towards the Pyla dune and stored around the pine trees surrounding the dune."