Architecture: A very smooth transfer...

A long strip of water no wider than a footbath inside the new Cathay Pacific lounge, which opened this week at Hong Kong Chek Lap Kok airport, is the most expensive piece of flooded real estate in the world.

It costs $10,000 a week to rent that channel within the gigantic 4,000 square metre complex that Cathay Pacific have taken over from the Airports Authority for First Class and Business travellers. They have spent $200m on a bold new airport lounge called The Wing, designed by minimalist architect John Pawson.

Those who adopt the Tara Palmer Tomkinson attitude to travel - never turn right at the top of the airport stairs - need an extra incentive to keep them loyal to business or first class or to upgrade to first. Now that all the major airlines have taken on board extra-outsize recliner seats, inflight entertainment, designer food and an Old World wine cellar, airport lounges are the next move to keep customer loyalty.

Minimalists never lounge. The very idea of sinking into soft upholstery makes these aesthetes spring to their feet. At home, John Pawson has benches: "For me, a bench is likely to be more satisfactory than a chair because a bench only does one thing, and it's always simple. Chairs are very rarely simple," he explains. The very idea of getting this perfectionist to design the lounge for Cathay Pacific in Hong Kong's new airport may seem crazy, but at least no-one can argue that Cathay didn't get what they wanted. When a team went from Hong Kong to John Pawson's practice in London two years ago to talk about the jewel in the crown of the new airport at Chek Lap Kok, John Pawson made the Cathay executives perch on long concrete benches. Only "the softies" plumped for the big leather pads that he calls cushions. It's been a learning curve for John, who installed in his artful installation of 508 chairs some 20th century classics which he has chosen for comfort - and just one example of his benchmark, the concrete slab seat.

"I designed this space which could feel personal to each and every person passing through it. I wanted to offer the international traveller the chance, however fleeting, to feel at home." As the designer of Calvin Klien's flagship shop in Madison Avenue and other shops around the world, John Pawson flies the globe and struggles to stay calm in what he perceives as the chaos of international airports.

Aviation may be 60 years old, yet most designers of airport lounges are still arrested in Las Vegas style circa 1980. Back-lit mini bars, claustrophobic clusters of vinyl chairs and tables, battalions of mobile phones recharging and stale peanuts is no incentive to keeping today's time travellers on seats. Or benches.

To call The Wing a lounge diminishes this awesome space. The floors and walls are great, grey granite slabs emerging from the white-painted steel and glass of the terminal building by Norman Foster. For weight reasons as much as fire risk, thin granite is veneered onto aluminium blocks - but even Stonehenge couldn't look more substantial than these thick cubes. Set about like children's building blocks they simply define, rather than enclose, different spaces they call PLS (personal living spaces). The Wing is not a hermetically sealed box. Work and seating areas flow seamlessly into one another, with restaurants, bars and working enclosures in between delineated by screens of shoji paper framed in concrete, and a long, opaque glass back-lit wall.

The effect is very calming. Pawson is a genius at lighting, using daylight from the top-lit Foster building, and diffused artificial light from hidden sources to play upon surfaces. For the first time Pawson uses colour - if you can call the mocha, espresso and cappuccino hues colourful - on capacious club chairs by Hoffman, Liagre and Wegner. But the only pattern he permits is the play of light and water upon hard surfaces.

Now travellers in Cathay Pacific Wings can shower or bathe when they arrive, have a shiatsu massage, get on-line, eat at the noodle bar, graze intermittently in one of the 20th century classic club chairs, or take a cocktail at the Long Bar in the slipstream of jets taking off soundlessly outside.

John Pawson describes Wing as an "oasis", though to the uninitiated that may seem like the equivalent of joining a fishing expedition in the Gobi desert. You need to experience the quality of space, which is the biggest luxury these days, with carefully thought-out details like the handle- free doors opening smoothly on hidden hinges, light only where it is needed, but always flattering light.

Floating in a soak-tub with just a paper-white narcissus and piles of white towels beside a long sleek pool, or showering in a cubicle with water pelting down as if the monsoon had started is all the more luxurious for being so simple. Simplicity is all about refinement and sensuality in the choice of materials.

Because the site is in Norman Foster's terminal, he admits that "it was rather like being asked to design an extension to a cathedral". Foster's Chek Lap Kok is one of the most beautiful airports in the world. In its vast, open interiors, crowds seem to vanish. The Wing by Pawson relates to Foster's building and gives it a much more intimate human scale, without actually reducing the scale at all.

What that egalitarian and libertarian design highlights under one soaring, glorious roof is that not all air travellers are equal. "Airside" (as airlines call that no-man's land between the departure gates and flight boarding) needs to be carved up so that gold card travellers who spend on an average 45 minutes waiting for flights - and pounds 4,000 for a return flight first class from Hong Kong to London - feel they are getting good value for money.

No sooner had the Pawson lounge opened than it became the subject of acrimonious debate, though everyone I saw there peacefully inhabited the space, either curled up and massaging their feet, reading papers, playing cards, sleeping, talking, working on lap-tops or eating in one of the noodle bars. John Pawson shrugs off comments about "mausoleums", admits that he can't do anything about "too much daylight" bathing the building (Norman Foster spent a long time getting it to do just that) any more than he can give them "a roof overhead" (ditto). Foster's high, top-lit roof is the airport's best feature and the Airport Authority certainly resisted any attempt made to tent it.

John Pawson is stung by all those who say it's cold (as in hard surfaces rather than temperatures). You can see why he minds. Minimalism is not sensory deprivation. Watching these hard surfaces come to life with reflections of water swirling like an animated Hockney painting that changes as the sun moves is anything but cold and lifeless.

The huge, back-lit Long Bar stretching 28 metres, that the American artist Dan Flavin would no doubt be pleased to have put his name to, has one of the best views of a city not short of them.

In the First Class restaurant, with its gently tapping water pool, hungry passengers can choose from a menu of oysters, caviar and sushi as well as hot meals.

"I'm all for water but frankly, it ought to have trout or ducks in it," says Sir Adrian Swires, chairman of the group that owns Cathay Pacific. He is unconvinced about that running water. It takes some nerve to pay those prices to put a strip of real estate under water and then watch business travellers getting their JP Tods wet when they inadvertently splash into the pool.

Initially a tad apprehensive of this ambitious venture, until he experienced the luxury of space that is beautifully reasoned and immaculately detailed - and comfortable - Sir Adrian is now a convert. "It may take a bit of time, but this is the way forward."

It's been a tough year for the Hong Kong-based Cathay Pacific who made a loss of pounds 13.8m over the six months ending 30 June this year, compared to a profit of pounds 84m in the same period last year. The airline blames the Asian crisis and air cargo problems at the new Chek Lap Kok airport as one of the reasons. The fall-off in Japanese travellers and the drop in tourism are also cited.

Would they commission the same architect to come up with the same design today? Peter Sutch, chairman of Swires and Cathay Pacific hesitates only momentarily. "Absolutely. With a few refinements, a little softening around the edges. Pawson wouldn't allow a plant in the place, you know."

These refinements include opening up another level below the cantilevered platform for a lounge with a low ceiling - isn't it astonishing that anyone would value a low ceiling in this age when space is the biggest luxury? - and a smokers' bar called the Runway, which is at present non-smoking.

About a year ago, when Cathay executives visited mock-ups of the Pawson design built in an engineering warehouse, they called for an urgent review. Why no colours, no plants, and so overwhelming in scale, they argued. Pawson added a little deep purple on the Christian Liagre chairs but couldn't be shifted on scale and proportion.

"That's what makes a space feel good to be in, that and the materials," he argued, and won. But at the launch party on 11 November he was cut out of the speeches, which was a shame because he was going to quote Ruskin on the subject of a railway station: "It's the very temple of discomfort, and the only charity that the builder can extend to us is to show us, plainly as may be, how soonest to escape from it."

That, and to remind us how, at the close of the 20th century, he has sought to create something which is everything the railway station in question was not. This project is not just another interior, but a building within a building, and a piece of architecture in its own right.

By stepping out of the white cube, John Pawson is moving into a new territory.