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

<p>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?</p><p></p><p>In the early 1960s, when Peter Zumthor was a teena