The river has its source in the Spanish Pyrenees (where it is called Garona), crosses the border into France and then flows northwest. Below the city of Bordeaux, it joins with the river Dordogne to form the great estuary Gironde, which flows into the Atlantic Ocean. Already in Roman times, the Garonne was an important traffic route through the province of Gaul for the wine trade. Along the banks of these waters lie many appellations such as Barsac, Cadillac - Côtes de Bordeaux, Cérons, Sauternes, Graves, Premières Côtes de Bordeaux and the southern part of Médoc known as Haut-Médoc.