The Brewery Oud Beersel, which started in 1882, is located in Beersel at 10 km from the Brussels city centre, in the southwest of the capital. It is one of the last remaining authentic lambic breweries of Belgium and well known for its lambic beer brewed along traditional brewing methods. Lambic matures up to three years in wooden barrels, whereupon it is blended to make Oude Geuze. Sour cherries undergo fermentation in lambic beer and after a second fermentation in the bottle Oude Kriek is born. This unique brewing process with spontaneous fermentation is possible in Belgium in the Pajottenland region, the Zenne Valley and in Brussels, because of the presence of a specific microflora.