Stretching from Pointe de Grave on the sea in southwest France about 80 km/50mi up to the city of Bordeaux, the Gironde Estuary is the largest in Europe. It is formed by the merger of the Dordogne and Garonne Rivers just below Bordeaux. The estuary varies from 3km/2mi to 11km/7mi wide, and its shores include some of France’s most treasured wine-producing lands. On the Left Bank are the Medoc and Graves regions, while the Right Bank includes the Libournais, Bourg and Blaye regions. Islands passed in the Gironde include the large Ile de Patiras with some vines and a lighthouse, Ile Sans-Pain and Ile Bouchard. Ile Paté is privately owned, and contains a ruined 17th century fort. The small Ile Verte, Ile du Nord and Ile Cazeau are left in their natural states as reserves for migrating birds. Ile Margaux is planted with vines, and is part of the Medoc wine region.