 The most expensive wines made from Riesling are late harvest dessert wines, produced by letting the grapes hang on the vines well past normal picking time. Through evaporation caused by the fungus Botrytis cinerea ("noble rot") or by freezing, as in the case of ice wine (in German, Eiswein), water is removed and the resulting wine is felt to offer richer layers on the palate. These concentrated wines have more sugar (in extreme cases hundreds of grams per litre), more acid (to give balance to the sugar), more flavour, and more complexity. These elements combine to make wines which are amongst the most long lived of all white wines. The beneficial use of "noble rot" in Riesling grapes was discovered in the late 18th century at Schloss Johannisberg. Permission from the Abbey of Fulda (which owned the vineyard) to start picking Riesling grapes arrived too late and the grapes had begun to rot; yet it turned out that the wine made from them was still of excellent quality.
