The lake of Grand-Lieu, located south-west of Nantes in Loire-Atlantique, is characterized by its very fluctuating surface during the year. In winter, the lake doubles in size. It then becomes the largest natural plain lake in France, sometimes exceeding 6,500 hectares. Due to its lush vegetation, its fluctuating water level and its classification as a nature reserve, it is often difficult to find access to the lake. In this article, we offer two unmissable viewpoints with free access to admire it and take a walk nearby.