Built on a rocky plateau visible at low tide and surrounded by shifting banks of sand, the Cordouan lighthouse is a monument that must be approached from the sea. It stands tall amidst sandbars at the point where the Gironde Estuary – which is shared by the Garonne and Dordogne rivers – flows into the Atlantic Ocean. As the first stage in our journey to Cordouan, let us get acquainted with this powerful natural environment.