The average Frenchman, the political saying goes, keeps his heart on the left, and his wallet on the right. Throughout this century the same has been true of Paris. The Right Bank of the Seine is the realm of power and money, the home of the President of the Republic, the Bourse, the best addresses in the 16th and 17th arrondissements, haute couture and the higher shopping.

Since the Middle Ages, the Left Bank has been the kingdom of the heart and the mind. Before the Revolution it was the realm of great abbeys such as Cluny and St. Germain. It is still the home of the university and of the most famous grandes ecoles. There are focuses of power on the Left Bank, among them the prime minister's office at Matignon, the Assemblee Nationale and several ministries. The old aristocratic quarter, too, the spiritual home of Proust's duchesses, was the Faubourg St-Germain.

But the Left Bank is par excellence the home of that endangered but tenacious species, the French intellectual. In the old days he came up from the provinces on a scholarship to one of the crack lycees, went on to higher education and there he stayed for the rest of his life, in and out of the cafes, the bookshops and the publishing houses, teaching, writing and arguing exhaustively, in print and face to face.

The publishers are still clustered round St Germain-des-Pres, taking their authors out to lunch at the Rotisserie d'en face. Students still throng the Latin Quarter, where Loyola taught in the 16th century, Aquinas in the 13th and Abelard in the 12th, where Villon and Rabelais, Rodolphe and Mimi from La Boheme misbehaved. Still, a great, probably irreversible, transformation is taking place in the social geography of Paris. The balance is slowly but unmistakably shifting back towards the Right Bank.

In part, this is the capricious movement of fashion. When I first visited Paris in the Fifties, St Germain-des-Pres was the centre of the Existentialist universe. Sartre and Simone de Beauvoir drank their coffee at the Montana. Sidney Bechet gave concerts at the Mutualite, in the same hall where the giant student demonstrations against the Algerian war took place, and someone in the Rue du Vieux Colombier had invented a new word: a discotheque, a bar where you could ask for records as you asked for books at a bibliotheque.

But a quarter of a century before that, Montparnasse, and in particular the four cafes at the intersection of the Boulevard de Montparnasse and the Boulevard Raspail - the Dome and the Select, the Rotonde and the Coupole - was the intellectual centre and night-life capital of the world. There you might see Hemingway and Gertrude Stein; Kiki, the model whose naked back appears as a violin in Man Ray's famous photograph; Matisse and Picasso, Modigliani and Chagall; and Sylvia Beach, whose bookshop, Shakepeare and Company, was down the road, calling James Joyce 'melancholy Jesus' behind his back.

Now fashion has moved on again. First, 15 years ago, the rebuilding of the central markets, les Halles, and the opening of the Pompidou Centre created a new vortex. Then the property developers moved in and revived the vogue for the Marais, the aristocratic quarter before the kings moved out to Versailles. Finally, the tide of fashion has washed past the Bastille into the 11th arrondissement, the onzieme, between the Bastille, the Place de la Republique and the Gare de Lyon. That is now, one young resident told me, le quartier le plus branche de Paris - the most switched-on neighbourhood in town.

Early in the century, foreigners and rich Parisians went slumming in the Rue de Lappe, home of tangoing girls and their knife- wielding Apache pimps. But since then, until the tide of fashion and speculation of the past few years, the area has been occupied by quiet tradesmen and craftsmen. Now the Balladjo nightclub has rock talent contests. There are foreign restaurants and endless art galleries, selling the New York mixture of photographs and mostly non-figurative painting. What finally switched on the Bastille and brought green shoots into the onzieme was the opening of the new Bastille opera for the bicentenary of the French Revolution in 1989.

The new opera house has not had very good notices, from lovers of opera or architecture. But it is one of the grand monuments with which first Valery Giscard d'Estaing, then Francois Mitterrand have set out to restore to Paris the grandeur of a great capital. It is hard to imagine John Major or Margaret Thatcher writing, as Mitterrand has done: 'The world moves, the city changes, under the impulse of forces which, left to themselves, would end up with the disorderly juxtaposition of nothing but private interests.'

Mitterrand has had no intention of leaving Paris to be moulded by private interests. It is these grand travaux, as they are called, the Great Works, which together are shifting the centre of gravity back towards the Right Bank. They are creating monumental buildings and whole complexes of buildings, in some cases whole new quarters. And they are endowing Paris with a new generation of public buildings, in the post-Modernist idiom, fit to rival the achievement of the belle epoque, and for which the only equivalents in London, appropriately, are those two monuments of the Eighties, Broadgate and Canary Wharf.

There are nine or ten Great Works, all but one firmly in the public sector, and all but two unapologetically cultural. The key to this cultural refit is le Grand Louvre. I M Pei was chosen to design the new approach to the museum through his elegant glass pyramid. But the real stroke was to kick the Ministry of Finance out of the wing of the Louvre on the Rue de Rivoli, enabling the whole palace to be used as a museum. Mitterrand has just opened a display of the museum's treasures of 17th- and 18th-century French painting; those of the 19th century are already on display in what was once the Gare d'Orsay, the first of the Great Works to be opened, in 1986.

Architecturally, there is little to be said for the new Ministry of Finance, into which 5,000 civil servants have been decanted to make room for the expansion of the Louvre. The same can be said of Carlos Ott's Bastille Opera and of the 'very big library' which the builders are racing to finish in the Rue de Tolbiac.

The Institute of the Arab World, on the other hand, is a small architectural jewel. Perhaps the Fifth Republic's motive in building it was impure: the desire to sell jets and helicopters to the masters of Islam. But the building, on a superb site opposite the apse of Notre Dame, is French elegance at its most pure. For its great south wall, Jean Nouvel, the architect, borrowed the moucharabieh, the screen that shields the windows of Arab houses from the light. He combined this with the technology of the camera shutter and the photoelectric screen to produce a wall of 240 panels studded with stainless steel apertures in the traditional shapes of Islamic architecture, roundels, stars and rectangles, which blink open and shut according to the available light. It looks magnificent.

The 'very big library' and the Institute of the Arab World, like the Orsay museum, are all on the Left Bank. But among the grand works, they are smaller ones. The two major projects, both in architectural and town-planning terms, are on the Right Bank. Each is big enough to pull economic activity towards it, helping to shift the city's centre of gravity inexorably.

In 1979, Giscard decided to use the forlorn 130-acre site of the biggest slaughterhouses and cattle- markets in Europe, at La Villette in the working-class north-east of Paris, for a museum of science. Under Mitterrand, and in the hands of the architect-in-chief, Bernard Tschumi, this has expanded and matured into the La Villette 'park'. The site is bisected by a canal. To the north is the 'city of music'. The Conservatoire has moved there. The Great Hall of the old cattle market, a magnificent 19th-century steel and glass building, has been transformed into a large space for exhibitions. And in the Zenith Paris has acquired its latest and biggest venue for pop music. All these elements are tied together by Tschumi's 'follies', rows of eccentric structures, some utilitarian, some fantastic, but all in the same warm cherry red.

The other side of the canal is the city of the sciences and industry, the largest science museum in Europe, more than 800 feet long, in a committed industrial post- Modernist idiom. Inside there are exhibitions, a library, conference facilities and the best science museum for children I have ever seen. Tiny children can be seen punching away at computers, timing themselves as they run past Olympic-style electronic clocks, taking TV pictures of each other and using an electronic robot.

La Villette pulls Paris towards the north-east and the economic activity generated by the motorway to Lille and Brussels and Charles de Gaulle airport. The counterbalancing pull towards the west, still on the Right Bank of the Seine, comes from the office development at la Defense. For 20 years French and foreign companies have been moving into skyscrapers: 14 of the 20 biggest French companies have their head offices there.

La Defense sits astride the great axis of the Louvre, the Place de la Concorde, the Champs-Elysees and the Arc de Triomphe at the Etoile, perhaps the grandest perspective in any city in the world. Even when it was seen as an office development, Pei proposed to close it with a pair of twin towers linked by an inverted arch. It was a Danish architect, Otto von Spreckelsen, who came up with the plan that has been built. It is called the Big Arch, but in reality it is a giant cube, its sides, top and base full of offices, but the centre open so as to conclude the axis of the Champs- Elysees without closing it.

From a distance, the Big Arch looks blank, a little like an enormous television set. But if you take the express Metro and walk up to the plaza, you realise that this is no longer a cold office development, a place where people work from nine to five - metro, boulot, dodo, (tube, work and crash); it has become a real, new quarter of Paris. There are art exhibitions, including a massive red sculpture by Alexander Calder. There are gardens, fountains, cafes, shops, cinemas, hotels and, behind the enclosing screen of coldly elegant skyscrapers, flats where 35,000 people live.

La Defense is about to acquire an even more spectacular monument. This is the Endless Tower, another brainchild of Jean Nouvel, a slender round tower, taller than the Eiffel tower, granite and glass below, steel and glass above, so that it will turn gradually from dark to light as it rises against the grey skies of the Ile de France.

Thirty years ago, when Jean- Luc Godard filmed Alphaville, his vision of the Paris of the future, he had to shoot it inside the airport at Orly; there weren't enough modern buildings in Paris to supply credible backgrounds. Now that has changed. The old Parises remain: Gothic, Baroque, the Paris of the Empire and the Third Republic. The Great Works may not all be unqualifiably great in themselves, but at least they have become the dramatic symbol and the entering wedge of a regeneration; driven by the ambition of successive holders of an autocratic presidency, and lavishly financed by the State, a new Paris is being born. Whether it will please as much as its predecessors is another story.


Accommodation: A lot of hotels on the Left Bank have modernised, without raising their prices too high. Two examples: the Hotel de Suede, Rue Vaneau, a quiet street between Montparnasse and the Faubourg St-Germain; and the Hotel Lenox, Rue de l'Universite, near St. Germain des Pres and the Musee d'Orsay. Another standby is the Hotel de la Place des Vosges.

Eating out: There are lots of good small restaurants in the 11th arrondissement. Try the Auberges Pyrenees-Cevennes near the Place de la Republique or Chez Paul, near the Bastille, or somewhere like Iguana, near the Bastille. The Coupole at Montparnasse is refurbished and reliable. The Dome, across the street, has a Michelin star now. Chez Lipp, at St Germain des Pres, is a brasserie beloved of politicians for decades; its sister restaurant, in the Rue des Ecoles near the Sorbonne is Chez Balzar. A personal favourite is Le Petit Lutece in the Rue de Sevres.

(Photograph and map omitted)