Single malt whisky is malt whisky from a single distillery, that is, whisky distilled from fermented mash made exclusively with malted grain (usually barley), as distinguished from unmalted grain. For more than 500 years barley and water have been the basic ingredients for single malt Scotch whisky. Scotland has unique water. Since there is no limestone, the water is very soft. The rain water flows over hillsides overgrown with heath and through peat meadows, thereby taking up the unique flavour typical for each distillery.