‘If it’s too slick, it looks like a fashion mag’: Peter Zumthor on his £110m rammed concrete gallery

It is one of the world’s finest collections, full of Monets, Miros and Picassos. But is the great Swiss architect’s extension for the Beyeler Foundation a worthy addition? Or is it a bit luxury boutique?In the early 1960s, when Peter Zumthor was a teenage apprentice in his father’s cabinet-making workshop, he designed his first cupboard. He later recalled the satisfaction of fitting the door so perfectly that it closed “with a special sucking sound”, saying his father instilled in him “the Basel pride in the well-built object”.Six decades on, with a fleet of globally celebrated projects to his name, the 83-year-old Swiss architect is back in Basel, beaming with the same local pride. He is gazing out at his latest well-built object, which is also his first project here: a monolithic new gallery that looks chiselled from the earth, its layers of pale crumbly concrete hammered into shape, its big oak and bronze doors – their handles wrapped with leather cord – closing wi