Come and see this", Renzo Piano says, and the 74-year-old Italian architect beckons me out of his office, through the front door, and on to the pavement. We're in the Marais district of Paris, and it's buzzing with early-evening life – shoppers, café denizens, office workers heading for the Métro. Piano – tall, slender and bearded, with a ducal air about him – walks a few yards and then stops and points towards something that's up a side street. "Look! Look!" he says, his eyes sparkling.
Look where? A dry-cleaners? A florists? An approaching taxi? And then I lift my gaze and realise what Piano is trying to show me. A couple of hundred yards away, filling the narrow horizon at the end of the street, is a bank of metallic, cylindrically shaped blues, greens, yellows and reds – a surreal sight that's instantly recognisable as a small section of the exterior of the Pompidou Centre. A big smile spreads across Piano's face. "Ah," he says. "Now you see!" In the UK, for reasons one suspects are rooted partly in patriotism and partly in ignorance, the Pompidou Centre, which opened in 1977, tends to be thought of as exclusively the work of its British co-architect, Richard Rogers. But it is as much Piano's work, and when he is in Paris – he also has offices in his native Genoa and in New York – he takes evident delight in being able to pop outside and remind himself of the revolutionary achievement that established him as one of the world's most skilled and imaginative practitioners of his craft.
The Pompidou commission came when Piano was only in his mid-thirties, and although he has been responsible for a glittering array of buildings in the 35 years since – from grand-scale projects like Potsdamer Platz in Berlin and the International Airport in Osaka, to such small, specialised creations as the Padre Pio Pilgrimage Church in Italy and a cultural centre on the Pacific island of New Caledonia – it is Beaubourg, as all Paris knows it, for which he remains most famous. That is, possibly, until now.
In a couple of months' time, a Renzo Piano building will open which, physically, will dwarf all his others, and may eventually be the one most people associate with him. The Shard – previously known as London Bridge Tower – became, as of December 2011 when it passed Moscow's City of Capitals' height of 990ft, the tallest building in Europe. It tops out at precisely 1,000ft.
A tapering glass structure that reaches up and up and up before melting into the heavens, its appearance and mood constantly changing with the light, the Shard would be utterly distinctive even if it stood amid the skyscrapers of Canary Wharf. But it doesn't. It stands in splendid – some would say stark – isolation on the site of London Bridge station on the south side of the Thames, where its impact is enormous.
After the Post Office Tower in the 1960s, the NatWest Tower in the 1970s and the Gherkin in the 2000s, the Shard is central London's latest skyscraper to turn heads, draw gasps, and divide opinion. London may not yet have learnt to love the Shard, but there is no doubt that it is beginning to impinge on the city's consciousness and assume a role of London identifier to rank with the most potent. It's perhaps no surprise that the Shard occupies such pride of place in the helicopter shots that make up the title sequence for the latest series of The Apprentice. As representative of London in 2012 as the Olympic Games, the Shard is the latest expression of a metropolitan dynamism that no global recession seems able to slow.
The combination of scale and location was always going to make the Shard controversial, and its development has been perhaps the biggest architectural debating point in London since Prince Charles complained about the "carbuncle" that was a proposed new wing to the National Gallery in the 1980s. A public inquiry in the early 2000s drew a range of opponents, notably English Heritage, which viewed such a vast structure as a disfigurement to central London's historic skyline. In particular, the Shard was regarded as an offence to St Paul's Cathedral, whose cherished outline, from whichever direction you looked at it, was irredeemably diminished by what lay just the other side of the river.
In the end the pro-Shard camp won the day. Ken Livingstone, then the Mayor, loved the idea of it so much that he said he wanted a second Shard. It probably helped that Livingstone's architectural adviser was Richard Rogers, who remains a close friend of Piano's and one of his most ardent champions. For Southwark Council, the Shard meant regeneration of the area on a spectacular scale (the project includes the transformation of London Bridge station). The developer, Irvine Sellar, brought the necessary energy, vision and financial acumen to proceedings, qualities he'd demonstrate a few years later when securing fresh investment in the project from Qatar at a time when, amid the economic crisis of 2008/09, it had hit trouble. And the then deputy prime minister, John Prescott, the man who had ordered the public inquiry, was satisfied that the Shard would fulfil the requirement of being built to the highest architectural standards.
So when Piano sits down in his Paris office and spreads out photographs of the Shard at various stages of its construction, he is entitled to feel proud, and not a little relieved, that more than a decade after he discussed the project with Sellar, it has finally come to fruition. That said, Piano feels he must defend the Shard, and he is especially sensitive to the argument that centres on St Paul's Cathedral.
I have always loved St Paul's," he says "St Paul's is an icon of mine because it is a great building. It's fantastic. But when St Paul's was built, it was modern, just like the Shard is modern now. It wasn't a classic at the time. It became a classic."
The Shard, Piano says, was about the "intensification" of the city. Yes, its height is extreme, but its footprint is relatively small and the way it combines a variety of uses, and, crucially, is open to the public, is what makes it special, and not to be compared with the financial institutions that typically occupy such premises.
When the project architect, William Matthews, took me on a tour of the Shard a few weeks ago, he pointed east to the skyscrapers of Canary Wharf and said: "We absolutely didn't want to build one of those – a great big American fridge." Instead Piano and his team have built a vertical town – with offices, shops, a hotel, restaurants, some private apartments, and, up on the 72nd floor, a viewing gallery.
That members of the public can access the top of the building is something that matters a lot to Piano and his team. They want Londoners to feel that the Shard belongs to them and that they belong to it. As a building that will draw visitors hungry to experience the most stupendous views of the capital and beyond, the Shard, says Matthews, is closer in spirit to the Eiffel Tower or the Empire State Building than it is to any commercial property.
"It's a very old dream of mine, this idea of making a building like a little town," Piano says. "So when people say, oh but it's going to use up so much energy, it's not true. An actual town of 8,000 people [the Shard's projected number of occupants] would use up five times as much energy. This is why the Shard is the shape it is. The higher up you go, so the functions change, and you need less floor space, until you get to the very top, and there I just wanted the building to kind of mingle in the air. It's important that it breathes up there – that it breathes in the clouds."
Another key idea informed the Shard's shape: the idea of the steeple, a design feature of which London enjoys a rich legacy through its churches. Among the things Piano wants me to look at is an engraving of 18th-century London which is dotted with church spires. The message is implicit: London is full of spires – the Shard is just another one. It fits in. Piano gestures like a conductor during a quieter passage of music. There is a lightness of touch about everything he does, and it's why the Shard may be one of the least macho tall buildings in the world.
Renzo Piano was born into a family of builders. A career in architecture was almost inevitable. "I've always loved to make things. I still do." Piano is known for the precision and beauty of his model-making, and the importance he attaches to laying out his projects in miniature. His Paris model-making workshop adjoins his office, and passers-by can look in through the window and marvel.
After studying in Italy, Piano came to London and met Richard Rogers. They had Italy in common (Rogers was born in Florence) and soon bonded. Their bid to build the Pompidou Centre was one of no fewer than 700 that were submitted. They were young and unknown, and to their amazement, they were chosen. "I think ours was one of the few bids that had this idea to create a piazza in front of the building," Rogers, who is now 78, told me. "We thought about the social implications of the project. We were quick on the uptake, but really we had more confidence than knowledge.
"Renzo is a humanist, a great humanist," Rogers continued. "He combines the social, political and the technological so brilliantly. He creates tremendous buildings." And does Piano mind that the reaction to the Shard has not all been favourable? "For the seven years it took to build Beaubourg, we were attacked left, right and centre," Rogers said. "I think that has hardened him to criticism."
Given the time that Piano spent in London when he was younger, it is perhaps a surprise that it took him another three decades before he produced a building here. The Shard was his first London commission, but in the years it has taken to build it, Piano has completed another London project – the office development that is Central St Giles on the fringes of the West End, whose bright colours echo the Pompidou Centre and hint at the playfulness in Piano's character.
There are clues to Piano's philosophy in the way he lives his life and runs his business. For such a globally renowned practice, Renzo Piano Building Workshop is unusually small in terms of numbers of employees. "My personal rule is a maximum of 100 people," Piano said. "Sometimes we have had to go over that. But if you are bigger, you lose control. I like to know the name of everyone who works in the office." (Two of his three grown-up children from his first marriage work in the business. From his second marriage Piano has a young son.)
Apart from architecture, Piano's great passion is sailing, and his buildings wouldn't be the same if that wasn't the case. "If you ask me what is a kind of constant with me it is this idea of making a building fly – creating something with zero gravity. Maybe this is why I love sailing so much. Sailing is not just about the wind, it is about the boat, and its buoyancy and its lightness, and maybe, yes, the Shard is like that."
The word Piano said he hated was "style". "I think it is a trap. But what I don't hate is 'intelligence' or 'coherence'. Because coherence is not about shape, it is about something stronger, more humanistic, more poetic even. I don't know, this all becomes a bit romantic, maybe I should shut up!"
In his heavily accented English, Piano talks a lot about the intangible qualities buildings can possess – their energy, their magnetism, the way they can transform people's lives without them necessarily noticing. "There are about 300,000 people a day using London Bridge station," he said. "If what we've created gives them a better experience, then that's great."
But Piano knows that, whatever he says, the Shard's success or otherwise lies in the future. "You know, the best architecture takes time to be understood. I don't know how the Shard will be thought of. In some ways it's a bit narcissistic to even think about it like that. But I would prefer people to judge it not now. Judge it in 10 years' time."