Sauternes is a remarkable region of Bordeaux whose wines, both sweet and unfortified, are unmatched by anything else in the world. It is the region's mesoclimate, in particular the proximity to The Garonne and its tributary the Ciron, which combine to create the ideal conditions. During fall, the cooler water from the Ciron meets the warmer tidal Garonne, causing mists to develop, blanketing the vineyards. The fluctuation between the humid mornings and warm drier afternoons provides the ideal environment for the benign fungus Botrytis cinerea, to thrive. The fungus consumes the grapes' water, concentrating its sugars and tartaric acid, which helps produce wines with beguiling exotic aromas and thick viscosity.