The shape of things to come: Rem Koolhaas's striking designs

Rem Koolhaas puts his mobile phone in the middle of the wooden café table between us, picks up two teacups and a glass of melting ice cubes, and arranges them in a circle around it.

The phone is barely visible. "So, this is the entrance here," he says, pointing into a tiny crevice between the cups, "and as you can see it's completely surrounded by other buildings, so from any angle you can only see fragments of it." The teacups represent the historic streets of Bank, in the heart of the City; the glass is St Stephen Walbrook church, designed by Christopher Wren and built in 1672. The mobile phone is playing the role of Koolhaas's new HQ for Rothschild bank, due to open next year. "It's a very nice site," he explains, lightly, in perma-ironic, Dutch-inflected tones. "Because it's such a dense site, it has an incredibly radical relationship with the city." Even more incredibly, when it opens next year the Rothschild building will be Koolhaas's first in London – even though he's lived in the city, on and off, since the 1960s, when he studied at the Architectural Association, just around the corner from where we're sitting on a sunny afternoon in Bloomsbury.

Koolhaas surely understates the importance of this building, which began life back in 2006, at the height of the boom. In the current climate, famous architects haven't had much to boast about. The calamitous effects of the credit crisis have wrecked the real estate industry and the economic underpinning of mega-projects. Architecture is a notoriously cyclical industry, but the current bust has hit the profession particularly badly. Most firms have laid off hundreds of workers as the stream of commercial clients and the speculators who finance their buildings dried up. Libeskind, Gehry, Foster – name any gilded name specialising in "iconic" towers – all have had prestigious projects either binned or put on hold. And although for most of his career Rem Koolhaas was, famously, an "unbuilt" architect, in the last decade his avant-garde designs were actually coming to life. Most notable have been Porto's concert hall, Seattle's Public Library, stores for Prada in Seoul, New York and LA, the 9-storey Wyly Theatre in Dallas, with its transformable auditorium, and the 54-floor CCTV building in Beijing – a mammoth structure resembling a twisted bridge – finished just in time for the Olympics.

His buildings don't swirl or blob like a Gehry or a Hadid. A Koolhaas building is often block-shaped, unprepossessing from a distance, but fun to interact with. In common with his starchitect peers, his designs are inevitably called "iconic".

But Koolhaas thinks this is a term that has lost its currency in the recession. "We've been able to step away from the iconic domain," he says, apparently relieved. When I ask him about the effects of the crash on his firm, he acknowledges that many projects in Dubai "went up in smoke". But the Office for Metropolitan Architecture (OMA), the firm Koolhaas founded in his native Rotterdam in 1975, has global tentacles. "Because we're in Europe, China and America, we can really see the inequality of different economic conditions. It simply moved its grip to regions less affected by the banking crisis, notably North Africa and Hong Kong, and we just opened a new office in Asia. We shifted rather than diminished." But besides shifting attention east and south, Koolhaas has also continued to move forward by diversifying his work – which isn't much of a stretch given that he, above all other architects, has always been engaged with work other than designing actual buildings.

Even after he won the Pritzker Prize 10 years ago, Koolhaas remained the maverick of architecture, a figure who refused to see his craft as a force for social improvement, but instead celebrated the chaos of urban life. His books were for a long time more famous than his buildings. His first, Delirious New York (1978), theorised on the subject of Manhattan's skyscrapers; an entire library of fat, frenetic and often very funny books followed, at least two of which have been counterfeited by fans in Iran and China.

Some years ago Koolhaas opened a separate think-tank company, AMO, (named as the mirror image of OMA) to focus exclusively on his non-bricks-and-mortar projects, from catwalk shows for Prada and Miu Miu to creating a plan for decarbonising Europe's power grid, a project for the EU.

So as other architects scrambled to diversify in order to keep their firms afloat in choppy economic waters, Koolhaas has simply continued the extracurricular work for which he's always been known. Yes, he tells me, there are surviving building projects, including an educational campus in Doha and a cultural centre on the West Kowloon campus in Hong Kong among others, but it can't hurt in the current atmosphere to be known as the guy who creates more than just vanity skyscrapers for ambitious city-states and corporations.

His latest mission is defending an unpopular cause: Dubai. "There is a massive sense of condescension towards the people there," he starts. More than any other place, to the Western media Dubai and the Gulf came to symbolise the hubris of the boom era. The schadenfreude response to Dubai's fall after 2008 is of a piece with anti-Arab sentiment, he believes, one that judges the Gulf to have been naïve in believing it could build world-class metropolises. "The speculation might have disappeared, but what remains there is nothing to be sneezed at. Fifteen years ago, Dubai was very modest. Now we have clear evidence of an Arab [version of] modernity. That in itself is a huge achievement."

Called Al Manakh (meaning both "market" and "climate"), the book is a collection of 140 articles and interviews about the situation on the ground. "Many [Western] people went there for the first time [after the 2008 crash] and saw it as something that happened in one go, and therefore representative of a contemporary absurdity. It was a patchwork of outrageous convictions, aesthetics, labour, religion... everything. But if you looked more carefully at each of those aspects, there's more to say." It's not the first time he has said the unsayable about Dubai: an earlier publication attempted to challenge criticism of a migrant underclass exploited by construction firms. In the latest book, one article examines how migrant workers from Kerala have transformed entire villages back home from pay earned in the labour camps. "Westerners don't really want to understand [Dubai]. But I think it's also part of a bigger Western trauma, which is that we are no longer in charge. We still try to maintain our status, but we've basically lost it."

Koolhaas believes his affinity with the Gulf region comes from a period of childhood spent in another Muslim nation, Indonesia. "It felt very familiar to me," he says. Although every architect you'd care to name went there to build unfettered symbols of wealth over the last decade, most producing work routinely described as highly vulgar, OMA's interest in the Gulf has not been purely commercially driven, he insists. "It wasn't just about [looking for] a situation to exploit, but as a form of engagement."

Beyond the Arabian Gulf, he argues, the crash of Western markets might have actually been a good thing for architecture in general, grown plump as it had with speculation and globalised aesthetics.

"We're very glad that what I call the "YES" regime – which means the Yen, the Euro and the US dollar – which began in the 1980s and that dictated every value in every country, has finally come to an end. And I think it's a very good thing that the state is becoming responsible again after a long time of deregulation.

"In architecture certain things have become possible again. I was giving a lecture the other day and I showed a really unglamorous picture of an architect in the 1980s, holding a blueprint, really badly dressed, and behind him there is housing being built, disappearing into the horizon. That kind of architect is almost unthinkable until recently, but maybe that is coming back. Now we're expected only to design "the exceptional" and, to me, that's very uncomfortable. In a serious climate, [people are] more susceptible to serious ideas."

Koolhaas glides easily between the construction site, the fashion catwalk, publishing and consulting on the development potential of entire nations. An unlikely new client is Libya, specifically "a subtle group of people around the [Gaddafi] son there who want to pull the country toward Europe." Koolhaas has been engaged not to build but to develop the Libyan Sahara for tourism: "It's preservation," he explains, if one begins to imagine mechanized buildings rising from the sands, "We don't always want to build. We've found ways other than building to address situations."

If his apparent omnipotence makes him the ideal consultant for ambitious leaders of developing countries, established Europe also wants Rem's opinion. This year he was engaged by the EU to join a think tank of 11 wise Europeans to propose "ideas for the Union by 2030," the results of which are to be presented to Herman Van Rompuy this month. ("I am pro a European army. Without it, Europe accepts a diminishing of its role.") Taking the EU in hand isn't new to Koolhaas; in 2002, AMO created a new flag for the community, a brightly coloured "bar code" that was a composite of the colours of every member state; Austria used it as a logo during its 2006 Presidency. As a longstanding consultant to the EU brand, what does he make of the forces that currently threaten to bring down the ideal of a rainbow superstate?

"The problem of Europe is that it has a structure that was initiated but never completed. It has been receded by stealth; originally, it was driven by very intelligent people who put something in place that worked on their terms. But now there is a new generation of leaders who are more involved in running their own countries. Europe became an alibi for what was a problem in those individual countries. The current situation is an outcome of that – there are no defenders, only critics. So it can no longer evolve. It's crystal clear to me."

It's easy to fall into wide-ranging conversation with Koolhaas, who at 64 works a disarmingly stylish look, in head-to-toe Prada, and a slender figure honed by a rigorous daily swimming schedule. He so obviously enjoys his role as intellectual-for-hire that often one can entirely forget about the buildings.

Seeded in the boom years, they are continuing to sprout up. Next year his design for a Maggie's cancer care centre in Glasgow will open, to be followed by a revamp of the Commonwealth Institute in west London. But curious pedestrians can already view his first British major building.

Intrigued by the design for Rothschild, as represented by teacups and a mobile phone, the day after our interview I take the short journey to Bank to see if there are any obvious signs of his new creation. Armed only with the name of a nearby lane, I'm concerned I might not be able to locate the site. I needn't have worried. When I emerge from the Tube at Bank, the roads are closed to traffic, enormous yellow low-loaders blocking the way as cranes are winched up into the sky, starting the final effortful months of "topping out" the tower.

Just as Koolhaas described, its position in the midst of the ancient city means it is only visible in glimpses. It's a building that doesn't so much alter London's skyline as colour in the gaps: a flash of pale greenish-silver glass seen down narrow Georgian streets. One of the greatest architects of his generation is finally about to make his mark in Britain. Just don't call it "iconic".

For further reading:

'S, M, L, XL' by Rem Koolhaas (Monacelli Press)