Sour beers are those that have been inoculated with wild yeast such as brettanomyces, or kettle-soured, where acid-producing bacteria are introduced for a shorter time in a controlled fashion. Examples of the first include monumentally complex and incredibly long-lived Lambics from the Senne Valley near Brussels, also blended to form effervescent Geuze, to Lambics sweetened by the addition of fruit. Flanders Red Ale is another speciality of Belgium, tart and refreshing with a hint of volatility and a glorious red hue. Kettle-soured beers are often no less delicious, including Gose wheat beers brewed with coriander and salt and light & lemony Berliner Weisse.