When a luxury label like Prada commissions an intellectual architect like Rem Koolhaas to reinvent its shops, the merchandise risks getting lost in its bold new box.

Just such a gamble has been taken at the unusual -- and very experimental -- Prada store that opened 10 days before Christmas in SoHo. Don't call it a flagship, it's an "epicenter" of the new cool. Mannequins guard the door in gold lame{acute} hipsters fresh from Miuccia Prada's spring 2002 collections in Milan. But visually and metaphorically, the bi-level emporium is dominated by the Dutch architect's abstract floor. Koolhaas calls it the Wave.

From the sidewalk at Broadway and Prince Street, the 23,000-square-foot space looks like any chic industrial loft. But inside, the floor -- a broad sweep of exotic zebrawood -- drops off like a stair-stepped cliff. Here and there on a dozen descending terraces, dainty shoes have been strewn to signal an avant-garde shoe department. The floor flattens out for a few yards in the basement (23 precarious aluminum and zebrawood steps down) before curving back up to crest at sidewalk level. That's where a glass fence defines a sort of scenic overlook. It also prevents inattentive shoppers from sliding over the edge.

"I tried to inject instability," says Koolhaas, "to make a radical space. You never know what you are going to get here."

In Prada's new land of Oz, a few buttons are pushed behind the scenes. A massive soft sculpture of Prada fabric swings into view overhead. Then a chunk of the Wave flips down to become a stage. Sweep away the merchandise, and the shoe terrace will seat 200. The architect has turned the sales arena into theater.

"It works like a shop," explains Miuccia Prada, as hanging industrial cages display her fashions like autobodies on an assembly line. "Even more important," she says, is the potential to attract young people through cultural happenings. She plans to launch movie screenings and music events next month.

Architects are taught to express civilization's accomplishments in public buildings that will last through the ages. Fashion is normally fleeting, consciously frivolous and expressly commercial. At Prada, Pritzker laureate Koolhaas has attempted to blur the distinction. He made the interior architecture as changeable as a hemline or lapel. He also gave the boutique a higher calling: The epicenter was designed as a place where commerce and culture can coexist.

"We were worried about the incredible commercial development of SoHo," says Koolhaas. "There was almost no public space left. This space can be in its entirety commercial. This entire space can also be a space for New York."

New Wave Shopping

The Prada-Koolhaas collaboration ranks among the year's most talked-about -- some say hyped -- design events. It is certainly among the most expensive: The company declines to reveal figures, and Koolhaas says he doesn't know how much the project cost, but unofficial calculations have veered toward $1,800 a square foot, or about $41 million.

Other fashion houses have opened design-driven flagship stores this year, from Giorgio Armani in Milan to Donna Karan and Issey Miyake in New York. But none has been accompanied by such grand aspirations: SoHo is the first of four planned "epicenters," two more by Koolhaas, in Los Angeles and San Francisco, and one by Tate Modern architects Herzog & de Meuron in Tokyo. And no other project has been preceded by such an elaborate rollout.

Last spring in Milan, Fondazione Prada, the fashion house's cultural wing, staged an exhibition of architectural models and prototypes to introduce the epicenter concept -- and the Wave. The foundation followed up with a glossy, image-filled tome titled "Projects for Prada Part 1." In it, Koolhaas and team reveal their plan to reinvent the Prada aura through design. As it says in the book, "Space is a marketing tool."

Through the 1990s, the Prada brand reigned supreme, a logo of cool for young, urban sophisticates, who traveled the world with trendy Wallpaper magazine stuffed in designer duffles. Then architect Frank Gehry created a seismic shift in design. After his Guggenheim Bilbao museum, wavy, deconstructed, titanium-clad architecture suddenly looked hotter than any runway show.

No fashion-business couple responded to the challenge like Miuccia Prada and her CEO husband, Patrizio Bertelli. Over a decade, they had propelled her family's leather goods company into a global fashion conglomerate, acquiring stakes in such high-profile labels as Fendi and Jil Sander. But as Bertelli tells it, he was awed by the power of the Guggenheim: Gehry's shimmering icon had turned a drab industrial city in Spain into a design mecca.

"He created a scene, not just a museum," says Bertelli.

Now, with Koolhaas, arguably the world's most fashionable architect, Prada has created its own spectacle. Outside the shop's front door, a familiar brand-name landscape is visible: Victoria's Secret, Armani Exchange, Dean & Deluca. A more elite style vortex is reached by the back stairs: the Mercer Hotel, Jean-Georges Vongerichten's Mercer Kitchen, and Canteen, with its Marc Newson interior. Armani Casa is on the next block, across from the influential Moss design shop. Prada hopes to differentiate itself with translucent polycarbonate walls and an interactive multimedia experience. Being at Prada is supposed to be as entertaining as buying.

For starters, the wallpaper will change with the seasons. A glass elevator 12 feet in diameter is stocked with handbags so customers can shop while descending to the bikinis. Down below, a black-and-white marble floor echoes home base in Milan. But intentionally distorted mirrors convert the classic checkerboard into a fun house.

"It's a space in which a new generation will find more stimuli," says Bertelli. "It's a new way of interpreting space."

Prada SoHo is fully wired. Computer monitors hang among the clothes racks to show fashion clips, search for merchandise or even link archly to eBay, the online auction site, where 2,447 supposedly authentic or frankly fake "Prada" items are also for sale. Radio-frequency identification tags tucked in tasteful black envelopes will keep track of who tried on what and where it went. A hand-held "staff device" developed by the IDEO design firm will let sales consultants order up customer histories, inventories, credit data and only Prada knows what else.

IDEO's research found that Prada customers reserve dressing rooms in advance and spend an average of two hours trying on gear. In SoHo, they will find changing rooms with glass doors that open and close at the touch of a toe. (Tap the black ball to lock, white to make the glass opaque.) A "smart" screen enables shoppers to hunt electronically for a different size or color, or view another collection. (A human being is still required to fetch.) A "magic" video mirror is programmed to capture the rear view. A shopper can spin around, then watch for a slightly fuzzy replay.

Waiting companions may chill out in three media alcoves. One offers a "peep show" of runway trailers, including models dressing backstage. Another provides vaguely spiritual reading and images. A third is strictly for Prada gazing, with global where-the-stores-are maps. We-are-the-world stats include Prada vs. GDP and Prada vs. Population.

The data have also been compiled in the "Projects for Prada" book, which notes that "Prada can be big in small spaces." Prada was big enough to let Koolhaas design a store in which all the merchandise, from dress racks to accessory displays, can be rolled out of sight when it's time for the Wave to open.

'Theorist and Prophet'

On opening night, guests in stiletto heels mince up and down the shoe terrace, but Koolhaas, 57 and clad in black, takes the steps two at a time.

A onetime screenwriter from Rotterdam, he acquired a near-cult following as the author of the books "Delirious New York" and "S,M,L,XL." Now he molds minds at Harvard's design school. On this day, he jots down talking points with a common red Bic pen and asks to be remembered as "a thinker," not the designer of a new generation of fashion boutiques.

"No, no," he pleads, adding, "there's a nightmarish tendency to overstate the importance of the architect." He diffuses credit -- and possibly defuses critics -- by limiting his contribution to "the ability to mobilize many different intelligences." (Twenty collaborating firms are listed for the SoHo project.)

But that's not how he won the Pritzker, architecture's most prestigious prize. Last year, the jury declared him to be a "rare combination of visionary and implementer, philosopher and pragmatist, theorist and prophet." His portfolio of built work includes a major urban complex atop a rail terminus in Lille, France, as well as a remarkably sensitive house for a wheelchair-bound client in Bordeaux, France, designed with floating floors instead of a closed-in elevator. The Koolhaas branch of the Guggenheim in Las Vegas juxtaposes high art and low culture, placing a replica of the Sistine Chapel in Casinoville. For the Dutch embassy in Berlin, a spiraling path through the building leads to a roof garden overlooking a river.

This month, Koolhaas was awarded commissions for a $250 million arts center for Dallas and a new Los Angeles County Museum of Art. His bold proposal for the latter -- demolish the existing campus and start fresh under a soaring translucent glass roof -- was described in the Los Angeles Times as "a critique of the entire history of the modern museum."

Before Prada, Koolhaas's Office of Metropolitan Architecture had not designed a retail environment. But Koolhaas was well-versed in the nature of shopping. His graduate students at Harvard had been researching the evolution of retailing over 800 years for their Project on the City. Their analysis has just become an 800-page illustrated book, "The Harvard Design School Guide to Shopping." Conclusion: Shopping is now "the defining activity of public life."

Ordinary mortals recognized that long ago, while circling for a space at the mall. But Koolhaas is focused on the architectural implications of globalization, or how the private economy has impinged on public space.

"The market economy of the past 30 years has more and more dictated our choices," he says. "The growth of stores has shifted cities away from public toward private environments. Retail gets built, but it also changes the state of the city. The irony is that shopping is a critical component of what is happening in the city, but it is rarely taken seriously."

His epicenter project for Prada has two more installments, though in the current economy, plans can change. For Beverly Hills, Calif., Koolhaas has designed a 21,000-square-foot glass cave on Rodeo Drive. In San Francisco, his proposed steel facade laced with portholes and nicknamed the "cheese grater" survived a challenge by preservationists after Koolhaas flew in to defend his design. Each will be unique to its city, making visits potentially as collectible as Prada bags.

Whether a Wave, a Cave and a Cheese Grater will be taken seriously is an open question. When Miuccia Prada knocked unannounced on Koolhaas's door in 1999, no one predicted that the New Economy would crash. Since Sept. 11, demand for luxury products has plummeted. At least a quarter of Prada's revenue comes from U.S. shoppers, and the company has acknowledged sales declines of 25 to 40 percent since September. In November, Prada sold off its stake in Fendi to raise cash.

"I don't think it's the end," says Koolhaas. "I think it's a course correction."

Some architects welcome a new direction. In the wake of Sept. 11, Alexander Gorlin, a New York architect, publicly dismissed designer boutiques "as matters of significance for architecture." In a letter to Architectural Record magazine, he argued, "Architecturally and culturally, this is clearly the end of the era of hyper-inflation of image and the blurring of architecture with fashion, shopping and other popular enthusiasms."

Gorlin reflected on his letter in a conversation this month, describing himself not as a lone voice, but as one "who had the courage to speak out." When commissions from a major fashion house could be treated like "the Second Coming," he warns, "we were at the crest of the superficial in architecture."

Prison of Sameness

When the Prada epicenter was finally unveiled to the media, the elevator wouldn't budge. The Hanging Sculpture got caught in the Wave. The Prada World Map glitched. The electronic dressing room door was not intuitive enough for two guests, who escaped only after pulling an emergency exit lever. And catering staff had to be stationed at intervals down the stairs so no one would topple headlong onto the shoe terrace.

Still, there were ideas with potential to have an effect beyond the SoHo changing rooms. Koolhaas and his team investigated how a global brand could escape its own "prison" of sameness. If epicenters work for Prada, could Starbucks and Wal-Mart decide to become unpredictable too? And would that be welcome or destabilizing?

The Koolhaas crew determined that routine dressing rooms were "hostile environments," and who would argue? Even without all the IDEO technology, a few more Prada-style gel-cushioned stools would be an improvement. The experts considered how to create "humane coexistence between store and customer" (but nobody mentioned lowering the prices). The greater goal was "letting the world enter the store." In the end, how widely the door is opened will say as much about the elite world of fashion as it will about the architect's design.

Miuccia Prada rides the Wave, descending the aluminum and zebrawood steps into Prada SoHo's shoe department.Rem Kohlhaas, below left, designed his Prada SoHo store so that computer monitors hang on the racks among the skirts and dresses.