Jean de florette

Instead of stone ashlar, a lush vertical garden cloaks the wing facing the riverfront. Photograph by Tim Crocker

What must rank as one of the most strange, wild and mysterious museums in the world opens today in Paris. It is a large complex on the riverfront a stone's throw from the Eiffel tower, yet it violently disrupts the city's close-knit streetscape. The competition-winning design is by Jean Nouvel, France's leading architect, yet it throws out virtually all his slick, hypermodern trademarks. It's as if France's answer to Norman Foster had suddenly transformed himself into a second Will Alsop.

Inside, outside and all round the building, a multitude of bizarre features jostle for attention. Three sides are surrounded by the instant forest of a park, and at one end the landscape actually climbs up the external wall to form a luxuriant vertical garden. The main facade facing the river is a curving wall from which project a varied assortment of room-sized boxes. Behind the curving wall is a six-storey glass cylinder stocked with musical instruments. As for the museum interior, it is an amorphous, gloomy space through which a dried-out river gully meanders.

But why such a radical departure from contemporary urban architecture? Can it be yet another case of a celebrity architect indulging his artistic whims? Well, there is method in this madness. The design rationale given by Nouvel is pretty straightforward - once the purpose of the museum is revealed, that is.

The Musée du Quai Branly is devoted to ethnological art. On display are black magic masks from Africa, richly patterned processional robes from Asia, fertility figurines in painted pottery from preconquest South America and even one of those enigmatic standing-stone heads from the Easter Islands.

The building, in Nouvel's words, is "a sanctuary for the scorned and censured works produced not long ago in Australia and America". After immersing himself in "obsessions of death and oblivion" and visions of haunted places "wherein dwell and converse the ancestral spirits", his response was to throw out his Western architectural vocabulary and its underlying philosophy of mechanistic functionalism. And if such standard features as curtain walls, structural frame, suspended ceilings and display cases must exist in the new building, he argues, "let them be out of our sight and mind; let them step aside from the sacred artefacts on view and allow us room for communion."

A bizarre assortment of boxes projects from the main museum wing Photograph by Tim Crocker

The result, continues Nouvel, is not archaism but ingenious new techniques that dissolve material form to give the viewer the appropriate architectural and mental space to view the many ritualistic and sacred objects. "Here, illusion cradles the work of art," he concludes.

Let architecture step aside from the sacred artefacts on view and allow us room for communion

The illusionary experience starts well before the visitor reaches the main entrance. What Nouvel has created is in effect an informal processional route that is packed with disorienting surprises - some solemn, others jokey - and delivers the visitor at the permanent collection in a suitably primed frame of mind.

As you approach the museum from the river, you walk along one of those splendid Parisian boulevards of London plane trees and come up against a sheer screen of clear glass that is a full city block long and two storeys high. The screen gives a full view of a long, five-storey facade that curves gently backwards. Out of this facade erupts an array of 30 rectangular boxes in a seemingly random variety of sizes and colours, ranging from light beige and grey to dark brown and mauve. If anything, it brings to mind the scattering of a child's wooden blocks.

You pass straight through the glazed screen by means of open gates at its midpoint. Suddenly, central Paris is left behind you and its traffic noise shut off. You find yourself picking your way through a secluded forest of low hillocks, winding paths, semi-mature trees and blood-red grasses. The forest-park sweeps beneath the museum building, which is raised up on columns, and spreads out another half block on the other side. As Nouvel explains: "The Parisian garden becomes a sacred wood and the museum dissolves in its depths."

The main entrance is in a conventional six-storey wing facing the street on the other side. But before you enter, glance upwards, and through the windows you can see exuberantly coloured and patterned ceiling paintings that are different on each floor and were commissioned from Aboriginal artists. Mirrors, which inconspicuously line the window, reveals and internal walls, reproduce the ceiling art to kaleidoscopic effect.

To suit the museum’s exhibits ...

After negotiating the main entrance, the ticket desk and the few steps to the main museum wing, you arrive at the start of a gently curving ramp, which continues for a further 180 m. The ramp leads you up and around a wide glass drum that is packed with musical instruments and rises as a see-through tower through the heart of the five-storey building. The ramp then snakes its way around the side of a lofty, curvilinear hall intended for temporary exhibitions. The white-painted concrete hall is brightly lit by a large window wall facing the forest park.

Finally, you emerge in the permanent museum, which stretches out the full 220 m length of the main wing. After the bright white temporary gallery on the floor below, your eyes must adjust to a mysteriously gloomy, cave-like space, where surfaces are painted deep mauve, the south-facing window wall is shrouded in dense brises-soleil and the opposite window wall is screen-printed in dense green jungle scenery. You are further disoriented by an uneven floor surface. Overhead float three curvilinear mezzanine floors and at random intervals beefy cylindrical columns pop up, some faced in clay and modelled into ethnic patterns.

Only the exhibits themselves stand out in the gloom - often with startling immediacy, spot-lit in floor-to-ceiling display cases.

Material form seems to melt away and we have the impression that the museum is a simple sanctuary without walls, set in a wood

Jean nouvel

Meandering through the middle of the exhibits is a what seems to be a dry river gully or Arab wadi set between shoulder-height earth banks. On closer inspection, the banks turn out to be remarkably accommodating. Instead of raw earth, they are faced in soft leather and have a set-back at rump level, so visitors can lean back comfortably to take a breather and view video programmes on small screens set into the opposite bank.

Finally, what about those diverse collections of boxes projecting out of the north facade? These turn out to be self-contained, pocket-sized galleries opening off the main museum space, each focusing on a particular group of exhibits. Like the beefy columns, the boxes are lined and decorated to match the exhibits they enclose.

Whereas the temporary gallery is a flexible loose-fit space, the museum floor and its display cabinets and projecting boxes have all been designed to fit the permanent collection as snugly as possible. This begs the question of how the curators will cope when they decide to replace the exhibits in a few years' time. The answer is that, with the wide diversity of display enclosures and the huge permanent collection of 300,000 objects on offer, they will have plenty of scope to choose the exhibits to fit the enclosures, rather than laboriously reshaping the enclosures to suit the new exhibits.

... the main gallery has a twilit interior and a row of projecting pocket gallaries. Photograph by Tim Crocker

One other mould-breaking public space worth mentioning is the large auditorium.

It takes the form of a 500-seat rectangular pit recessed into the basement floor, but its space whooshes out unhindered on three sides into adjoining foyers and bars, as well as through sliding glass doors to a small external amphitheatre.

The secret ingredient here is a thick purpose-designed acoustic curtain that can be drawn around the auditorium. This arrangement offers several options for performance space, ranging from small and focused to large and inclusive and, with the sliding doors drawn back, even including the external amphitheatre.

What, then, is the verdict on Jean Nouvel's magic wonderland at quai Branly? Do the contortions of modern building technology provide a genuinely stimulating experience that puts visitors in the right frame of mind to absorb the non-Western art displayed inside? Or are they just an irritating architectural distraction? Worst of all, do they amount to no more than a high-brow theme park, in which twee "ethnic" scenery is bogusly and patronisingly contrived?

Isabelle Guillauic, who headed the project team at Ateliers Jean Nouvel, is perfectly clear about the distinction. "We have tried to evoke the objects on view, not mimic them," she says. Certainly, the landscaping and building forms evoke a strong if remarkably varied non-Western character without Disneying the forms of ethnic architecture. But at the end of the processional route, when the visitor is confronted with the brightly spotlit exhibits, these theatrical props recede into the dimly lit background leaving behind the strange, disturbing ambience they have created. In Nouvel's words: "Material form seems to melt away and we have the impression that the museum is a simple sanctuary without walls, set in a wood."