Peter Zumthor unveils £110m Beyeler Foundation extension in his home city of Basel

Swiss architect Peter Zumthor, 83, has completed his first-ever building in his home city of Basel: a roughly £110m extension to the Beyeler Foundation in nearby Riehen. The foundation, which houses the art collection of dealer Ernst Beyeler and his wife Hildy — including works by Monet, Miró, Matisse and Picasso — was originally designed by Italian architect Renzo Piano and opened in 1997.

Zumthor was chosen for the commission in 2016 from a shortlist of 11 architects, after 100 were initially approached. The new gallery rises on the site of the formerly private Iselin-Weber woodland, which has been incorporated into the museum grounds, nearly doubling the campus. Alongside the gallery, Zumthor designed a five-storey, timber-clad office and art-handling building, plus an auditorium pavilion intended as a free, ticketless public lounge.

Concrete mixed with local limestone

For the exterior, Zumthor used his trademark "rammed concrete" — a rough, hand-tamped mixture blended with Jura limestone and laid in daily layers of no more than 45cm, leaving visible seams between pours. He has previously used the technique on the Bruder Klaus field chapel in Germany and a holiday house in Devon.

The interior departs from Piano's bright, top-lit galleries next door: the ground floor has a darker, cave-like quality, while upper floors feature large windows looking out towards the Black Forest and the Jura mountains. Asked about the concrete's carbon footprint, Zumthor said the material gives classical art the "substance" he believes it needs, which he argued a timber building could not provide.

The project is the subject of a new documentary by Wim Wenders, From Inside Out. It follows Zumthor's previous commission, a $724m extension to the Los Angeles County Museum of Art.