Lakeside spectacular.

Dominated by a vast, copper-clad roof and a series of layered and juxtaposed planes, Jean Nouvel's cultural centre on the edge of Lake Lucerne fosters culture as public spectacle.

Lucerne is known for its staggered timber bridge and Belle Epoque hotels set against the lake called Vierwaldstattersee and a backdrop of Alpine peaks. Since the railway arrived in the last century, tourists have used this compact city as a base for exploring the surrounding landscape and as an affluent cultural venue. Now Lucerne's new Cultural and Congress Centre (KKL) launches the city into the next millennium. Designed by Jean Nouvel, it is perhaps his most impressive performance to date. The KKL rehouses Lucerne's long-established classical music facilities, its various conference facilities and a museum of contemporary art beneath an astonishing copper roof.

The KKL's roof sets a datum between the intimate scale of the city and the majestic presence of nature. In profile, it reads as a single green line 23m above the lakeside jostle of boats, jetties and ticket stalls, cantilevering out 45m to its north-east corner. Lined with matte grey aluminium, the soffit is dappled with reflections from the lake, from a gushing 1930s fountain and from twin channels of water that lead deep inside the building. If Nouvel's section is breathtaking, his plan is comparatively simple. A blue-panelled pavilion screening the Concert Hall, a dark grey box with twin exposed stair towers and a lucid geometric cage are parked beneath the roof as objects on display. To the rear, Nouvel's roof folds down as a perforated screen to the building's service areas.

The KKL has had a complex history. Nouvel won the original competition in 1989 with a linear roof over the city's Kunsthaus (since demolished). He placed the main auditorium at an angle out into the lake and intensified the nautical allusions by streamlining this principal hall as a sleek ship. For some time, however, an alternative scheme - that of third-placed Swiss architect Rudolph Luscher - seemed to supersede Nouvel's in the ambitions of the Lucerne authorities. When Nouvel returned to the project in 1992, the idea of building in the lake had become politically unacceptable. In response, he decided to divert the lake water across the public piazza to channels deep inside the project and sustain the memory of the shipyard that once existed on the site by treating his programmatic components as vessel-like volumes.

The razor-sharp, 12 000 sq m canopy is a reinterpretation of the classic portico as both urban symbol and public meeting place. It creates a new type of urban space Europaplatz - a parvis shaded and protected from rain and snow, but open to panoramic views and accessible at all times. Of the three primary volumes, the glass and aluminium box nearest the train station and mediaeval bridge is the busiest and most transparent throughout The day. It houses a restaurant, offices, museum entrance and various conference functions behind its decorative grilles. In the far flank of the KKL looking east over the lake is an elegant cafe, the Seebar, at piazza level and runs of enclosed corridors above, giving access to the Concert Hall behind. Here, Nouvel's copper roof also reaches out above a small, venerable local boat club.

The Concert Hall and smaller Middle Hall share a formal entryway within the pavilion (blue outside, 'Bordeaux' red inside) on Europaplatz. A double stairway criss-crosses itself to rise through four levels of foyer with a glass-enclosed lift at either end. Views out are through large and rectangular windows with canted jambs framing postcard-like images of Lucerne and its hinterland. The Concert Hall is a molten hull of red maple veneer, a gorgeous, contiguous surface. Being separated slightly from adjacent floor planes increases its legibility as a vessel in dock. The pavilion's fourth floor is an expansive open terrace with the roof's overhanging rim drawing a low line over the spectacular views (like a giant baseball cap). The Meeting Hall also has a terrace, but at first floor level to serve as a performance for public events.

By isolating programmatic elements, Nouvel is able to introduce channels of water from Europaplatz and zones of natural light filtering in from the roof soffit, enlivening the foyer space with catwalks and chasms. The monolithic copper roof is punctured in places, especially above the art museum. The museum (which will not be completed until late 1999) promises to be a calm, introverted space lit only from above. Its 2400 sq m exhibition area expands in simple orthogonal cells from the upper reaches of the western block across the Middle Hall. But the strategy of free-standing elements is also of significant acoustic benefit. Working with Russell Johnson of New York-based acousticians ARTEC, Nouvel creates acoustic privacy or independence for the Concert Hall by conceiving of it in this sculptural way.

From the tiered foyers, the curvaceous body of the Concert Hall recalls both a boat and musical instrument. Nouvel inverts that initial reading by lining its innards with thin balconies or gangways, the liner's viewing decks rediscovered inside the hull. That the Hall can accommodate all kinds of musical and oral presentations is due to Johnson's contribution. In essence, the chamber is the traditional shoebox with a high ceiling; it digs down to the first basement level to give the interior increased height. Below an organ loft, the orchestra platform is lined in a pale timber; most other walls are fitted with plaster tiles (60mm deep and 200mm square) on hinged convex panels. Together, the architect and his acoustician experimented with these white indented blocks producing five versions subsequently arranged as a functional mathematical ornament.

The team convinced the Lucerne authorities to reduce the Concert Hall's capacity from 2000 to 1840 places - the optimum figure for mass clarity - with each seat individually focused on the conductor. The convex wall panels open to a surrounding reverberation chamber which adds 7000 sq m to the Concert Hall's 18 000 sq m volume. Nouvel and Johnson also designed curtains that slide out from wall pockets and a circular floating canopy of timber strips which can be lowered or raised to effect the necessary difference in reverberation, for instance, a rousing romantic symphony and an intimate poetry reading. A memory of Nouvel's initial proposal to line the chamber in blue velvet survives in the dark ceiling plane studded with a constellation of tiny light sources.

Jean Nouvel has spoken for some time about his interest in film. At Lucerne, the magic of the copper roof is in part due to the lack of visibly supporting columns and walls. The various chambers do indeed hold up the roof which itself slopes back to a height of 3m. However, the experience of being within the KKL is to float cinematically between volumes and connecting views almost as if gravity no longer applies. The copper roof signals the KKL, but glass is its most important material. Without the horizontal and vertical transparency gained by layering and juxtaposing extensive planes of glass, Nouvel's architecture could not possibly be so changeable, so memorable and so inviting to passers-by. With a total expenditure of 205 million Swiss francs (almost half in direct funding from the city), Nouvel's KKL has met Lucerne's ambition to foster culture as a continuous public spectacle.

Architect

Architectures Jean Nouvel, Paris

Project team

Jean Nouvel, Brigitte Metra, Marie-Helene Baldran, Didier Brault, Sandro Carbone, Gunther Domenig, Xavier Lagurgue, Denis Laurent, Philippe Mathieu, Eric Nespoulous, Julie Parmentier, Matthias Raasch, Markus Rothlisberger, Beth Weinstein, Stefan Zopp

Structural engineers

Electrowatt Engineering, Pluss + Meyer

Services engineers

Schudel + Schudel, Aicher, De Martin, Zweng, Balduin-Weisser

Electrical engineer

Scherler

Acoustic consultant

ARTEC

Theatre consultant

Jacques Le Marquet

Photographs

Paul Raftery