This a favorite of mine - Oude Geuze from 3 Fonteinen just south of Brussels, Belgium.
It's made using a very unusual process - very old hops are used, so there's no hop flavour - they're only used for preservation. The fermentation uses wild yeast and bacteria which simply drop in from the environment. There's no pitching of cultured yeast as happens in normal brewing, so it's generally brewed in autumn when it isn't too hot. The resulting beer (lambic) is then aged in wood barrels and finally different ages of lambic are blended and bottled. Younger lambic provides some sugar, so it referments in the bottle giving a champagne like fizz. It's sour, tart, funky and super refreshing!
It's a fantastic, artisanal product and now the name "Oude Geuze" is protected under EU law, so can only be produced in or near to Brussels.
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