The Payottenland district west of central Brussels is home to lambic beer, the world's oldest beer style. These beers are made with a good portion of unmalted wheat, aged hops and once the unfermented beer has been boiled, they are left in vast open "cool ships", often in the dusty attic of the brewery, to cool overnight before being put into wooden barrels to ferment. These barrels are usually old sherry or port barrels but these days, brewers are experimenting with all sorts of barrels. The beer is then left to ferment for anywhere from 4-5 months to years whilst a complex series of reactions and fermentations happen amongst the wild yeast and the bacteria.
Young lambic beers are very dry, very acidic and reminiscent of cider. Mature lambics are more mellow and often have a fruit aroma even with no fruit added. Brewers do though often add fruit to these beers to add some flavour and take the edge off the acidity.