The largest sweet wine area in the Loire is the Coteaux du Layon designation, which stretches from Rochefort-sur-Loire southward for 50 km on either side of the Layon, a tributary of the Loire river.
The micro-climate on the slopes of the Loire river and its tributaries provides ideal conditions for these wines. The exceptionally high sugar concentration of the grapes is the result of two phenomena: the drying on the vine during the sunny autumn days, and the formation of Botrytis or noble rot. The first phenomenon is rarely possible on the Loire banks, Botrytis on the other hand, is more common.