1. A 1771 map (Carte des Gouvernments de la Flandre Françoise, d’Artois, de Picardie et du Boulenois, assujettie au Ciel et Projetté par Mr Bonne Mtre de Mathematique) shows the Aa separating Flanders not from Picardy but from Artois near the sea. The source of the Aa is given as in Boulenois, shown as a region in Artois, and it flows into the North Sea (on the 1771 map, into the Pas de Calais). In 1985-1995 the Aa was one of the most polluted rivers of France. The construction of a nuclear power plant at Gravelines in the late 1970s and early 1980s, with six reactors the most powerful in Western Europe, has completely transformed the landscape where the Aa reaches the sea.