From the roadside of the Mas d'Agnon, it is possible to observe the the Grand Mar swamps. They are located north of the Vaccarès pond, which is nicknamed "The Grand Mar" since it is surrounded by the Rhone and the Mediterranean. These freshwater and rice swamps are home to many nesting birds such as herons, stilts, but also water warblers and terns. This is the area of ??Camargue most important for nesting Purple Heron.