One afternoon, when the architect Daniel Libeskind was working in his Berlin studio, he placed a spherical teapot into a plastic bag and dropped it out of the window. He watched as it smashed in the courtyard four floors below. He then collected the fragments and began slowly, with great difficulty, to reassemble the shattered teapot.

“I wanted to see how it might look once all the pieces were put back together,” Libeskind explains. “When you’re designing a building, the experience is kinetic. You cannot always put something into words; otherwise you will simply produce a verbal diagram. You must feel your way towards your finished design. It’s not until much later that you’re fully aware of what you’re doing.”

The smashed-teapot experiment eventually formed the basis of Libeskind’s design for the Imperial War Museum North, which opened in Manchester’s Salford Quays in July 2002. A fissured globe that suggests the interconnecting shards of a world broken by war, the building confirmed his reputation as one of the most provocative and artistically ambitious architects in the world today.

From the outside, the museum-a centre-piece of Manchester’s recent revival-has a metallic impregnability, as if there were no natural point of entry. It seeks to unsettle you, forcing you to address the purpose and nature of a museum of war. Its aluminium-clad roof is constructed over a concrete base. Yet when the light falls on the curved, grey-blue shards of its exterior, the effect is surprisingly soft. Inside, that effect changes. You are made to feel uneasy-as you are when you first enter Libeskind’s career-making Jewish Museum in Berlin-by the curvature of the floor, the echoing spaces of the main exhibition hall and the vertiginous elevator shaft that carries you up to a viewing platform to look down at your fellow visitors 100 feet below, or out across a bleak cityscape. You feel, at times, as if you are being bullied by the building’s hard, confrontational geometry. This is a museum of war all right-the exhibits represent all aspects of warfare from primitive weaponry to the high-tech virtual conflicts of today-and Libeskind never allows you to forget that.

“It’s not that I want to bully people,” he told me. “It’s more that I don’t want them to be anaesthetised. I want them to be immediately aware that they’re entering a condition of tension.”

In the months preceding the opening of the Manchester museum, Libeskind had prepared himself for another awkward encounter with those of his British critics who, in 1996, had denounced his spiral-shaped design for an extension to the Victoria & Albert Museum in London. Because of the projected cost and internal problems at the V&A, the extension may never be built, although it received planning permission from the usually conservative borough of Kensington and Chelsea. Back then he was accused, by William Rees-Mogg amongst others, of being a ruthless experimentalist intent on destroying the traditions of British architecture. But to the V&A trustees, and many architecture critics, the self-supporting “spiral” designed by Libeskind would provide a spectacular sculptural presence arrestingly out of sync with the surrounding Victorian grandeur of South Kensington. For now, the design seems destined to remain little more than a gesture of bold intent.

The Manchester museum, by contrast, has been generally well received but, as with the Jewish Museum in Berlin, one of the chief criticisms was that it succeeds less as a museum than as work of sculpture, that its conceptual strangeness and monumentality overwhelms the often mediocre exhibits themselves. But, according to the architect Richard Rogers, Libeskind’s work isn’t just formally arresting-it is intimidatingly smart. “There are comparisons of course with Frank Gehry, in that they both favour very dramatic, sculptural forms,” he told me. “But Daniel, I think, has a greater analytic ability. When you first look at one of his designs, you often think that this cannot be built, this is an impossibility. But he has this knack of ... making the whole thing work. With someone like Daniel, so energetic and full of ideas, there’s always likely to be the shock of the new, which explains the reaction to the spiral design. But that’s a feature of the history of architecture-Christopher Wren’s design for the dome of St Paul’s Cathedral, for example, was turned down three times before it was given the go-ahead. Daniel is in the big league now. We’re going to get used to his style.”

The latest project on which Libeskind has been working is his design for the rebuilding of the World Trade Centre in New York. After a first round of six proposals were rejected as insufficiently ambitious last July, the Lower Manhattan Development Corporation (LMDC) invited seven architectural teams to submit more daring proposals, both for dramatic new buildings to replace the twin towers and for regeneration of the entire urban space. Libeskind was asked to submit his proposal by the LMDC’s head of planning, Alex Garvin, following a private meeting at last autumn’s Architecture Biennale in Venice.

After much secrecy and speculation, his design is currently on display, at the Winter Garden of the World Financial Centre in New York, along with designs from the six other teams, which include some of the world’s most renowned architects: Norman Foster, Richard Meier and Peter Eisenman. At the public unveiling of the designs in December, Libeskind proved himself characteristically adept at telling his audience what it wanted to hear.

“I arrived by ship to New York as a teenager, an immigrant,” he said during his presentation. “My first sight was the Statue of Liberty and the amazing skyline of Manhattan. I have never forgotten what that sight stands for. This is what this project is all about.” Many of the great buildings of New York-the Chrysler, the Empire State-belong not to the street but to the sky. The intention of the Libeskind design, which he calls “Memory Foundations,” is that, against this trend and to a greater degree than any of the rival proposals, its emphasis is on both the street and the sky, the future and the past. In fact, it goes beneath the street, taking the visitor deep into Ground Zero, to the original foundations of the excavated site. There is also a proposal for one 1,776-foot tower at the northwest corner of the site, a symbolic structure, containing a series of landscapes within its open trusswork. Commercial and cultural buildings would be placed to the east while, at ground level, Libeskind proposes putting a marker in the pavement for each of the rescue organisations that responded on 11th September, making the site what the New Yorker described as “a latticework of commemoration.”

Libeskind is not, in fact, part of a conventional architectural competition, although it must feel like one because of the covert jostling for position and simmering rivalries. The LMDC had initially planned to pick and choose between the invited architects, absorbing the best of each into a new composite design. It is now acknowledged that this is unrealistic but there remains disquiet both within the LMDC and more generally amongst some New Yorkers that Ground Zero is in the process of being transformed into an atrocity exhibition, a playground for advanced architectural taste. Yet a single commanding architect is likely to emerge and Libeskind has a serious chance.

He is undaunted by such a task. “The site no longer really belongs only to local planners,” he says, “it is now a part of an emblematic reading… of the world as it is developing into the future. The design and the rebuilding of the World Trade Centre site has to be a spiritual process, not only an architectural one. It’s not only about finding the visible angles, but the angles in the soul.”

A former academic, Libeskind is often mocked for his abstruse thinking and grand abstractions. His architecture is saturated in arcane references and his prose can be wilfully opaque. In person, he is an engaging, if erratic, conversationalist, operating in a swirl of great names, half-remembered quotes and excited allusion. As we walked one afternoon down a busy street near the V&A, I asked how he settled on the concept of a spiral for the museum extension. “I didn’t start with the notion of a spiral; it’s just that you suddenly realise what you’re trying to do and you name it,” he says. “Once you realise it’s a spiral-or a globe, as with the Manchester project-you have a clear guideline for what you’re doing, whereas before it was just undefined patterns. That’s why the broken-teapot experiment helped me so much: the world really has been damaged by war, not just physically but metaphorically, too, and I wanted people, through my design, to feel something of that damage.”

Before Daniel Libeskind, 56, won the competition to design the Jewish Museum in 1989, he had never built anything at all. He had spent most of his career as a theorist, restlessly moving from one country to another. According to the architecture critic, Charles Jencks, those were his “wilderness years,” when “Daniel was putting messages into bottles and sending them out to sea, but no one was picking them up.” In truth, Libeskind refused to build anything until he had found an opportunity equal to his ambition, perhaps an indication that he is more calculating than he appears.

Part of his initial problem in finding the right commission was the complexity and obscurity of much of his thinking. Libeskind, says Jencks, “was too hermeneutical in the wrong way-esoteric, private, hermetic. Many people thought he was a phoney. And then, miraculously, he won the competition for the Jewish Museum. It almost never happens in architecture that the right man wins the right competition at the right time.”

When he won the Berlin competition, Libeskind, his wife Nina and their three children were living in Milan, where Daniel was teaching at the Architecture Intermundium. In architecture, to win a competition is hard enough; to have your design then turned into a finished building can often prove impossible. Libeskind knew that if the museum was ever to be actually built, he and his family would have to move to a city and country about which, as Jews, they felt ambivalent. They arrived in Berlin on 4th July 1989, four months before the collapse of the wall.

“It required an enormous leap of faith as a family to cancel all future projects on the spur of the moment, to come to Berlin,” he says now. “But I felt that I had to do it. It felt like a mission.”

From the outside, the Jewish Museum resembles a huge concrete pillbox, fortified, like the Manchester museum, with mere prison cell-like slits for windows. Again, there is no easy point of entry-you go in through the adjoining baroque building, the original site of the old Berlin Museum, from where an underground tunnel leads you, in near-darkness, into the actual museum, which is structured as a zig-zag, a kind of stretched and unravelled Star of David. Running through the museum is a series of empty spaces that Libeskind calls the “embodiment of absence.” The most startling of these is the enclosed concrete of the “Holocaust tower,” which is neither heated in winter nor cooled in summer, and which on one wall has a symbolic ladder, a potential route of escape leading nowhere. The tower is claustrophobic and oppressive. The architecture critic Martin Filler described it in the New Republic as the “most affecting memorial chamber of modern times.”

There is no question about Libeskind’s personal investment in the project. More than 80 members of his extended family were murdered by the Nazis, which perhaps explains why he is so drawn to architectural works of public mourning. “I grew up with no aunts or uncles, no cousins and grandparents,” he says. “You recover, but you cannot forget.” His parents, Polish Jews, survived the war only by fleeing east into Russia, where they were interned and sent to Soviet central Asia. At the end of the war, they returned to Poland. Daniel was born in Lodz in 1946, a devastated city around which communism was tightening oppressively. The family emigrated to Israel when Daniel was 11; two years later, they moved again, this time to New York.

The Jewish Museum first opened to the public, without exhibits, in 1999, and such was its immediate impact that there was an expectation that it should remain permanently empty, a statement of historical discontinuity. But Libeskind says he never intended to construct “a bare building as a sculpture. Through being empty for so long, the building became too fixated on the extinguishing of Jewish culture.” Instead, he was determined that the building should embody hope as well as loss. “I wanted to show that Germans and Jews were part of one culture,” he says. The museum does, indeed, convey a feeling for the joint German-Jewish inheritance; but it is the sense of rupture which dominates.

Libeskind makes various claims for allegorical references and allusions contained in the museum. “Among the influences on the building are Walter Benjamin’s book One Way Street and Schönberg’s opera Moses and Aaron, as well as cabbalistic rituals,” he says warily, as if reluctant to expand or explain. How do these ideas manifest themselves? “Well, never explicitly. The best works of architecture have many layers; they’re not just about surfaces… It’s the same with, say, the mirror fugues in Bach’s Toccata in D minor. This piece of music has the most complex mathematics; the main theme is a meditation on the composer’s own name-B A C H. It’s ingenious, because that’s his signature, as it were. But most people are oblivious to this: they just listen to the music.”

Libeskind’s Bach allusion is not a casual one. Music is important to him and not simply because of the old cliché of architecture being frozen music. He listens to everything from classical to rap. Indeed, music is the reason his family moved to New York; at 15, the young Daniel won the America-Israel Cultural Foundation Scholarship for the study of music. A peer of Daniel Barenboim, he was a virtuoso concert pianist, who performed several times at Carnegie Hall. “I earned more money as a teenage pianist than I do now as an established architect,” he says, laughing. Strangely, however, Libeskind abruptly stopped playing in his late teens. He has never satisfactorily explained why.

“For me playing music was an interpretative event, the interpretation of something that was not mine,” he says. Perhaps the truth is that he has no idea why today he refuses even to own a piano. He did, however, offer one oblique clue to his thinking when he mentioned to me, in passing, that one of his favourite novels was The Loser by the great Austrian nihilist Thomas Bernhard. The Loser tells the story of a talented young student pianist named Wertheimer who one day happens to see Glenn Gould performing the Goldberg Variations in Salzburg. Wertheimer is crushed by the experience because he knows he will never be as great as Gould and that, if he cannot be great, he would rather be nothing. In despair, he commits suicide.

Perhaps Libeskind knew that, like Wertheimer, he would never fulfil the promise of his exceptional childhood and, as a self-styled optimist, embraced the theme of the book by renouncing performance, while at the same time ensuring that his own personal story had a different ending. Either that, or he was playing with me when he mentioned Bernhard’s novel-the kind of allusion-filled game that seems to inspire much of his work.

In his Berlin studio, Libeskind oversees a growing empire. He now employs a multinational staff of 60. During my time there, his staff was working in separate teams on a variety of competition-winning designs and commissions, including one for an extension to the Denver Art Museum, which is projected to open in 2005; a shopping and residential complex near Bern in Switzerland; the V&A spiral; a $200m design for a glass-walled extension to the existing stone of the H-shaped Royal Ontario Museum in Toronto and a graduate school for the University of North London (now called the London Metropolitan University) that Libeskind surprisingly described as one of his most challenging projects, precisely because the budget, at a little over £1m, is so small.

“Architects with big reputations are expected only to take on the lavish, attention-seeking projects,” he says. “But I think it’s very important to do smaller, more modest projects, especially those that are socially and culturally significant.”

The London Metropolitan University is located on the Holloway Road. It is a polluted urban landscape of ill-conceived concrete high-rise and low-rise buildings. Perhaps its very ugliness was what attracted Libeskind in the first place. “When I visited the university, one student told me how on seeing the place for the first time she couldn’t stop crying at the thought of having to spend three years there,” he says. “And yet it’s an excellent school. So the challenge for me is to create a building-for gallery space, seminar rooms and a café-that can help to transform the atmosphere of this section of the Holloway Road.”

He begins rendering an impromptu sketch of the Holloway extension-all curves and difficult angles-before being distracted by one of his staff entering the room, from whom he requests a cappucino. Observing him at work, discussing ideas for the Denver extension and other projects, it is hard not to be impressed by the boisterous democracy of his studio. There is a constant exchange of ideas between Libeskind and his team of young, jauntily-dressed architects: all gelled quiffs, bespoke specs and eccentric shoes. Even the youngest of them seems relaxed about sharing his opinion on the latest designs and projects. Neither Daniel nor Nina his wife (who handles most of his business affairs) has a fixed office; they share a desk with two secretaries.

There is an otherworldly edge to Daniel Libeskind’s voice, as though he were speaking through a vocoder. If you close your eyes, you could almost be listening to the synthesised voice of Stephen Hawking, only at treble speed. Nina says he is unwilling to engage with the usual details of the architect’s routine, such as speaking on the telephone-which he never does. “Most big architects do a sketch and then hand it over,” she says. “But Daniel doesn’t work like that: he’s interested in the process of building, in every detail right down to the smallest door handle.”

He is also, of course, a conveyor of ideas. Consider his first finished building, the Felix Nussbaum Haus, which opened in July 1998 in the northern German city of OsnabrÜck. Nussbaum was a German-Jewish painter who spent the early years of the war hiding in various houses. As the Jews were first ghettoised and then began to disappear, Nussbaum withdrew even further into anxious seclusion, retreating into smaller and ever more confined spaces. He was eventually betrayed by a neighbour and died in Auschwitz. As you walk through the Nussbaum Haus, the rooms reflect the narrative of the artist’s life: the further in you go, the smaller and more claustrophobic they become. The paintings are hung at increasingly more difficult and peculiar angles; sometimes you have to crouch to look at them.

“At times, he was hiding in what were no more than cupboard-sized rooms, his face pressed to the wall, but he still continued to paint.” Libeskind had characteristically high ambitions for his building: “I wanted the building to be about memory and loss, but also about the future and a spirit of optimism.”

It is hard to share his optimism when you visit the Nussbaum Haus or the Jewish Museum: the sense of loss is too great. And yet you believe Libeskind when he speaks of his belief in the future. In the act of creation he is seeking to transcend loss. “For this reason, I wouldn’t call him an elegist,” says Rogers. “The sculptural quality of his work and his background may suggest that he is building epitaphs. But he’s not looking for that association.”

The success of the Jewish Museum has liberated Daniel Libeskind. He now has the public profile and audience he once feared he would never find while he laboured in academic obscurity, and the means and support to turn his ideas and concepts into buildings. Will he be compromised by the fame and wealth that will inevitably follow? What will happen to him if he is commissioned to build on the World Trade Centre site, presently the greatest prize in contemporary architecture?

When I was with him in Berlin, he listened patiently as I outlined the familiar criticisms of his work: that he has too many conflicting ideas; that his virtuosity irritates as much as it enlightens; that the star system in his profession can lead to ever more ludicrous and ostentatious forms of public display; that his extreme shape-making appeals only to those interested in postmodern theories of architecture.

“I completely reject the notion that there are too many ideas in my work,” he said. “Architecture is nothing if it is not about ideas. As for the star system and the desire to shock, I’m not part of that game.”

There is a danger, perhaps, that Libeskind’s reputation has peaked (he is already widely imitated, for example by Peter Eisenman’s austere, and unfinished, Holocaust memorial in Berlin, or Melbourne’s Federation Square, a cultural space reminiscent of the Jewish Museum) and that he will start to take on too much, as if trying to make up for the lost period when his projects had no chance of being built. Some well-wishers fear that he will enter too many competitions and end up exhausted by his schedule of meetings and travel, and by the grim compromise of modern architecture, the trade-off that is required between the architect, his collaborators and the assorted local politicians, financiers and town planners if a building is to be completed. One wonders, too, if the architectural language that was so appropriate for the Jewish Museum is equally applicable to Libeskind’s Swiss shopping mall.

“There are many problems with architecture, not least those with costs,” Libeskind says. “But if something is worth doing, it’s worth doing well. I believe in public projects and I believe that there is an ultimate meaning to history. We die, yes, but tradition and culture are immortal. I work within a great tradition. I believe that to build something is to believe in the potential for a better future. So, for me, architecture is the most optimistic of all professions.”

A couple of days after my last meeting with Libeskind in London, I received a phone call from his Berlin office. “I have Daniel on the line,” a voice said.

“But I thought he didn’t make phone calls,” I said.

“Well, he’s on the line.”

I had asked him about a recent invitation he received last year to propose ideas for a memorial to the 1994 Rwandan massacre. In the light of this, the Jewish Museum and the World Trade Centre competition, I wanted to know if he was concerned that he might end up becoming caricatured as the architect who memorialises death and genocide.

“I have been thinking about what you asked me the other day,” he said. “I think I have an answer. So long as you are always doing something new, something different, always experimenting, no matter what you’re designing-be it a shopping centre, museum or memorial-then you can never allow yourself to be caricatured or stereotyped in any way. At least, I hope not. The Rwandan project is very challenging because I don’t want to design a conventional memorial. I’m visiting Rwanda soon, and hope I will return with some ideas that will enable me to do something entirely new, something true to the local culture. I have no wish simply to build a mausoleum.” With that I heard a small, anxious laugh, and he was gone.

“Despite what happened to his family, Daniel believes in the power and creativity of humanity,” his wife, Nina, told me over lunch at the Jewish Museum. She and Daniel met for the first time in late adolescence at a summer camp in upstate New York for the children of Holocaust survivors. Nina is, like most of her family, tough, political and determined-her father, David Lewis, led the New Democratic Party in Canada, and her niece is Naomi Klein, author of the anti-globalisation polemic No Logo-but she is also candid and likeable. “I’m always amazed by how positive my husband is about even those issues that would depress most people,” she said, as we returned to the studio.

Daniel Libeskind, I realised, is a religious artist; not a believer in any conventional sense, but an architect with a singular eschatology all the same. He has his own sense of sin and salvation. He would agree, I think, with Milan Kundera that the struggle of the individual against power is the struggle of memory against forgetting-and in that struggle lies his optimism. The danger of his being caricatured as an elegist, as little more than a specialist in memorials to suffering, may yet also lead to his greatest opportunity. For what does Ground Zero require, if not a specialist in architectural memorial?