The glass cabin is furnished with four director's chairs - two on one side, which face out to sea, and two on the other, which face towards the cliff. Put a table in the middle and you could have a bridge four. It's all very civilised.
But there's something about not quite being able to believe where you are that keeps you on your feet. Is this thing safe? It would feel blase to sit down - as if this were just any old train journey, and you were on your way to any old office. And the view across the Mediterranean - well, you have to remain standing if you really want to appreciate it.
Progress up the cliff face can only be described as stately. Under a clear blue sky, thick vegetation and patches of rock give way to a well- tended, terraced lawn, and above it a broad, handsome pale-wood building with a solar-panelled roof and a riot of botany within. When the cabin comes to a gentle halt and the transparent doors slide open, you are put in mind of one of those scenes when James Bond is welcomed into the villain's lair. As with a Bond film, all sense of reality has been suspended.
I am on my way to meet the architect Renzo Piano - "perhaps the world's greatest" according to his fellow-practitioner and long-time associate Richard Rogers. And this private funicular railway, which is the only way of reaching the utopian headquarters Piano has built for himself a few miles outside his native city of Genoa, is just the sort of touch that has won Piano his many admirers. Piano's combination of function and fantasy, of craftsmanship and inventiveness, has earned him a status within the profession that equals if not exceeds that enjoyed by more celebrated names such as Frank Gehry, Daniel Libeskind or our own Sir Norman Foster.
There is a good reason why Piano, who is 65, is not as well known in Britain as he might be: he has never designed a building here. He was living in Britain 30 years ago when he and Rogers got together and came up with the Pompidou Centre in Paris, a landmark for which the credit so often seems to go to Rogers alone. Piano went on to complete dozens of other projects - on the Continent, in America, in the Far East, in Australia, even on an island in the Pacific Ocean. During that time, Britain moved, somewhat tentatively, towards embracing architectural modernity, but it never acquired a building by Piano. Now, at long last, that could be about to change. And when it does, it will do so in spectacular fashion.
Later this month, at Bankside House near Tate Modern, a public inquiry will be held into London Bridge Tower, a Piano creation which at 1,016 feet would make it the tallest building in Europe, some 200 feet taller than Britain's current tallest - Canary Wharf in London's Docklands. The size alone is enough to mark London Bridge Tower down as special. But Piano has gone far beyond an exercise in height for its own sake. He has done nothing less than rewrite the language of skyscrapers as it came to be laid down first in Manhattan in the 1920s and 30s and then, in the second half of the 20th century, all over the industrialised world. We know what skyscrapers are about, don't we - money, power, sex and all the aggressive rest of it. With London Bridge Tower, however, we must think again.
The immediate purpose of London Bridge Tower, it has to be said, is somewhat mundane. The developer, Irvine Sellar, plans to give it over mostly to office space, with a few floors for apartments. But in appearance, it is anything but. For a start, London Bridge Tower, to be sited to the south of the bridge, right next to London Bridge tube and railway station, is not an oblong. It tapers to a point where it appears to dissolve into the atmosphere. "The tower is designed to be a sharp, light presence in the London skyline," Piano explained in the proposal for the building, "generous at the bottom without arrogantly touching the ground, and narrow at the top, disappearing in the air like an 18th-century spire or the mast of a tall ship." Highly appropriate though these analogies are for a building that will occupy a historic site overlooking the Thames, neither has stuck. Among those already familiar with London Bridge Tower, it has come to be known as the "shard of glass", a sobriquet which may not be preferred by Piano but which serves him to the extent of acknowledging that he has created something with edge as well as elegance.
Will the shard of glass, which is expected to cost pounds 500m, get the go- ahead? Those in favour of it, who are in a sizeable majority and include the Mayor of London Ken Livingstone, say they are quietly confident that it will. Those against say they are quietly confident that it won't. One view is that it probably will win approval, but that Mr Sellar will simply take the opportunity to sell a site that will then have become much more valuable. Naturally he denies this, and Piano stresses the agreement that he and the developer have drawn up which commits the architect to the project, and to its highest possible specifications.
Irrespective of the outcome, the inquiry will mark a pivotal moment in the history of London planning, offering high-level discussion of what kind of city we think it is, and want it to be. And about one thing there will be no disagreement - that if London does want to take a bold architectural step forward, then it couldn't be in better hands than Renzo Piano's.
Those hands are long and slender, and don't rest for long before they are at work with pencil and paper. Mr Sellar recalled his first meeting with Piano to discuss London Bridge Tower, in a restaurant in Berlin. "He picked up the menu and immediately started drawing," Mr Sellar said. "Piano had the idea straightaway." "I sketch all the time," Piano says as we sit at one of the many circular tables dotted about his open-plan office, where meetings of other members of the Piano team convene and break up and convene again in an apparent spirit of free-flowing creativity.
Earlier I had watched Piano, a tall, ducal figure, taking part in one of these meetings himself. "He's a very good listener," I had been told by Peter Buchanan, the author of a number of books on Piano's works. Here was the evidence: the bespectacled Piano, a benign, attentive presence, not noticeably leading the discussion but sitting back with his arms folded, occasionally stroking his salt-and-pepper beard. "He's devastatingly charming," Buchanan had said, "and very intimate in small situations. But there's never an innocent situation with Renzo. He's always negotiating." Paul Finch, the chairman of the Commission for Architecture and the Built Environment (Cabe), which has worked closely with Piano on the London Bridge proposal, said that when Piano entered a room he "brought a bit of magic into it". Piano might yet charm his way to securing the future for London Bridge Tower.
The son of a Genovese builder, Piano liked nothing better as a boy than to rummage around on his father's building sites. "When you admire your father, it is a natural thing to do," he said. "That was when I learnt that architecture is not just the art of putting up, it is the art of putting together." Piano has held good to those principles, and in a gesture to his artisan roots he has called his company the Renzo Piano Building Workshop. It has an office in Paris as well as the one in Genoa.
After studying in Milan and jobs in Philadelphia and London, Piano made his breakthrough when he designed the Italian Industry Pavilion at Expo '70 in Osaka. His partnership with Richard Rogers followed, and with the Pompidou Centre, completed in 1977, on his cv, Piano could go almost anywhere. And anywhere was where he was in demand. "Renzo's buildings are more diverse in character than anybody else's," says Peter Buchanan. "They resonate with the local culture to an extraordinary degree."
This makes it difficult to define exactly what a Piano building is, and without one grand statement to his name to rank with, say, Gehry's Guggenheim Museum in Bilbao, he has had to settle for a reputation for versatility. But all his buildings, no matter what size or shape they come in, retain a sense of humanity that gives them instant appeal.
A checklist of his most important projects shows Piano's range. There is the Bari football stadium, built for the 1990 World Cup in Italy; Kansai International Airport in Osaka; the Museum for the Menil art collection in Texas; a redevelopment of the old port in Genoa; a large section of the rebuilt Potzdamer Platz in Berlin; the Padre Pio church in Foggia; and the extraordinary, egg-shaped cultural centre in New Caledonia. Piano cares enough about the centre to keep a scale model of it on display at his Genoa office.
Piano's technical skills are clearly without compare. But he also talks a good building. "He's very persuasive, a brilliant presenter of thoughts and ideas," says Richard Rogers.
Now Piano is presenting his vision for London Bridge Tower. There are two aspects to it - the design of the building itself, and the effect it will have on the environment around it. Piano believes he is on to something with the tilted glass panels that make up the exterior. "It will be atmospheric," he says. "It will reflect the weather and the sky - it will change in appearance thousands of times every day." He explains that the problem with tinted glass - the choice of many skyscraper designers because it "stops heat gain" - is that it makes buildings look forbidding, and "a bit mysterious". Piano doesn't want mystery. He wants openness. Meanwhile, his solution to the heat problem is to create a system at the top of the building akin to a car radiator. The wind will do the rest. London Bridge Tower, says Piano, is "about balance and about lightness".
If anybody could be said to have added a touch of lyricism to skyscraper design then it is Piano. But why the shape? "With office space, you want the widest possible area. But with living space you don't need those kind of dimensions. So we put the living space higher up, and so we can go smaller, and smaller. It makes complete sense."
Even the project's detractors can find little in the building's materials and design to complain about. The argument really begins over the scale of it, and the consequences that follow from having a building like this in a place like London Bridge.
Prominent among those in favour of London Bridge Tower is the local authority, Southwark Council. A few weeks ago, its head of regeneration, Paul Evans, took me on a tour of the proposed site. "I haven't been down here for a while," Mr Evans shouted above the wind and clamour of trains and traffic. "It's good to remind myself just how nasty it is." We stood at the foot of the building that London Bridge Tower will replace, Southwark Towers, an undistinguished block that is presently home to an office of Pricewaterhouse Coopers. "We wouldn't miss that," Mr Evans said.
Anybody who has used London Bridge station, which stands to be transformed by the tower, knows what a complicated, user-unfriendly place it is, and would welcome a complete overhaul. Piano's plans envisage a new concourse that occupies 40 per cent more space than the present one. But Southwark is just as interested in what the tower will offer in terms of yet more prestige in a borough that is already revelling in having Tate Modern. Mr Evans also pointed out that sections of the borough are still among the most deprived in the country, and "London Bridge Tower will bring us huge economic advantages. The City has no scope for further development. But we have so many links to the City that it makes sense for us to be the City on the South Bank."
Both Richard Rogers, on behalf of the Greater London Authority, and Cabe's Paul Finch will be giving evidence to the inquiry, and have their own reasons for supporting it. "In the first place, the best locations for high-density buildings are around transport hubs," Lord Rogers said. "And in terms of hubs there's not a better one than this. The idea is that everybody using the tower will have arrived by public transport. There won't be any car parking. Second, it's a run-down area that badly needs upgrading. Other parts of the South Bank represent probably the best example of regeneration anywhere in England. With London Bridge Tower, the process could be turned into a continuous flow." And of course, Rogers loves Piano's building. "It could be the best building in Britain. Which is not to belittle St Paul's Cathedral. That's still the best 300-year-old building in Britain. But London Bridge Tower could be the best modern one."
Mr Finch said Cabe had "no problem with the height or the form. We think it's got the makings of a world-class project." What does concern him is the area immediately around the base of the building, which he thinks could offer more by way of public space. "We want something that will benefit everybody, not just rail users."
The question then arises of the building's relationship to the narrow streets nearby, some of them dating back to medieval times. Joe Kerr, an architectural historian at the Royal College of Art, is worried. "It's hard to suggest that London Bridge Tower has really addressed its locale. For my money it's a problematic scheme. But then I'm not at all in favour of London becoming a city of tall towers. I prefer the Parisian notion of pushing it all to the periphery. We have towers going up at Canary Wharf, and that seems to me to be a more environmentally acceptable solution, away from the overcrowded centres." London Bridge Tower will, in effect, create a new town of 8,000 people within Southwark, but when I put this to Paul Evans, he just said, "Well, new towns are being created in London all the time."
Mr Kerr won't be addressing the inquiry. But English Heritage will, and as a statutory body its objections will carry clout. In 1991, English Heritage drew up its "Strategic Views" - 10 London views of St Paul's and the Palace of Westminster which it seeks to protect from adulteration. London Bridge Tower falls foul of two strategic views looking south from Hampstead Heath, one from Parliament Hill, the other from Kenwood.
"We're delighted that Southwark Towers is going to be demolished," said Nicholas Antram, English Heritage's assistant regional director for London, "but we feel that what is going in its place is going to be so dominant that it will make St Paul's look like a toy. You've got Guy's Hospital with 18th- and 19th-century buildings, seen in juxtaposition with a building of gargantuan scale. We think it's a damaging contrast in scale."
Rogers says that English Heritage "has not evaluated the quality of the building", adding that "there's always this natural reaction against anything new". Mr Antram points out that English Heritage supported the Swiss-Re building across the river - the acclaimed "gherkin" designed by Sir Norman Foster - which he says proves that it's far from innately conservative.
Renzo Piano steers a diplomatic path between these two standpoints. "I'm very used to such situations. But it's good to have English Heritage saying these things, because it challenges you to understand what you are doing. If you gave me a job and told me to do what I wanted, I'd be frightened. It would be too complicated. You badly need the continuous discussion with other people. This is not about tactics, it's just about understanding, and understanding is listening."
You would think there wasn't much more Piano had to learn. Not so. "Life is short," he said. "I guess you need at least 60 years to live, then you need at least another 60 years to give to architecture, and then another 60 years to teach it to somebody else. You can't do everything." Piano does find time to sail - there's a model of his ketch on the wall behind him - and for his family, the three grown-up children from his first marriage, and the three-year-old son, Giorgio, whom he has had with his second wife.
It's the possibility of making new discoveries that seems to keep Piano going. He even revealed that as a young man he had wanted to become a journalist. He numbers many musicians and writers among his friends, including the Peruvian novelist Mario Vargas Llosa. I spoke to Llosa about Piano. "I think it's very rare for a famous person to be so modest, so devoid of arrogance or vanity," he said. "I think Renzo feels rewarded in what he does. He enjoys it so much, and he doesn't need to waste time being arrogant or frivolous." Piano's choice of friends, Llosa said, reflected his curiosity about the world. "He's not secluded within his own professional horizons, and I think that's a source of inspiration for him."
Is London ready for Renzo Piano? That may be a test of its own horizons.