A "Düne" is a hill or ridge of sand formed by the wind, typically found in coastal areas or deserts. These natural formations occur when sand is blown by the wind and accumulates in certain areas, creating a mound. Dunes can vary in size and shape, and they play an important role in protecting coastal ecosystems and preventing erosion. Dunes are often home to unique plant and animal species that have adapted to the harsh conditions of shifting sands. They can be found in various locations around the world, including the Sahara Desert and the Great Sand Dunes National Park in the United States.