From Lime Ventures:

“Cantillon is the only traditional lambic brewery located within the city of Brussels. Founded in 1900, today Cantillon operates both as a brewery and as a living museum, the Brussels Gueuze Museum (Musée bruxellois de la gueuze). Cantillon uses 100% organic grains and hops in all of its beers. Cantillon brews traditional lambic products, using 65% malted barley and 35% unmalted wheat. Cantillon’s beers are spontaneously fermented using a large coolship in the attic of the brewery and fermented in oak barrels.”

Links to more info about Cantillon: