Cagnes-sur-Mer is a French Riviera town near Nice that is in the Alpes-Maritimes department, in the Provence-Alpes-Côte d'Azur region, in s…Cagnes-sur-Mer is a French Riviera town near Nice that is in the Alpes-Maritimes department, in the Provence-Alpes-Côte d'Azur region, in southeastern France. Cagnes-sur-Mer is a town in southeastern France on the shores of the Mediterranean Sea between Saint-Laurent-du-Var and Villeneuve-Loubet. The largest suburb of Nice, it stretches along a cove offering nearly 4 kilometres of beach and is surrounded by hills, including the one of the castle, which rises to 91 metres above sea level.