Veiled in emeralds: Zürich museum

Like many museums and galleries the world over, Museum Rietberg in Zürich needed more space. The trouble was that the grand Italianate lakeside villa didn’t really lend itself to an extension – and certainly not in the proud Swiss tradition of rigorously functional engineering and purist modernist architecture.

The answer was to build a £19m precision-engineered modernist glass box, but as a standalone pavilion 100m to one side of the villa. How neat, and how very Swiss – even if the architects that won the design competition were the Austro–German joint venture of Krischanitz & Frank of Vienna and Büro Grazioli of Berlin.

Yet this pavilion counts as an extension because it has an underground connection to the classical villa. In fact, the pavilion is nothing more than a spacious, daylight-filled entrance foyer. Within it, a narrow staircase leads down to two basement floors that stretch back towards the villa.

These floors turn out to be spacious art galleries in their own right. They are entirely artificially lit, but this is not really a problem as Rietberg’s priceless collection of antique Chinese and African sculptures, paintings and ink drawings all require dimmed lighting, free of ultraviolet rays, as well as constant temperature and humidity.

Coming back upstairs from the basement, you notice that the severe flush walls and the glass roof of the pavilion are actually bright emerald and highly ornate. This ornamentation is the antithesis of sculptural modelling. It is a complex, repetitive, pattern of tiny opaque green triangles fritted on the glass, that shimmer like an array of facetted precious stones.

In fact, the architects says the design concept was inspired by the image of “canopies of emerald”. This occurs in a poem that was written by Mathilde Wesendonck, the first occupant of the villa, and set to music by Richard Wagner.

A rigorously modern building, then, but one suffused with highly romantic undertones.