Ciron, river or stream which rises on the eastern edge of the forests of the Landes in Gascony. It flows north-west and crosses the Sauternes region (see Sauternes AOC) and joins (as a tributary) the Garonne river at Barsac (see Barsac AOC), downstream from Langon. The moisture it brings, especially morning mists, promotes the development of the noble form of Botrytis cinerea (noble rot) which contributes to the high quality and renown of the sweet white wines of Barsac and Sauternes. The Garonne flows into the Gironde estuary onwards to the Atlantic ocean.