The Pompidou Centre shocked critics when it opened 30 years ago. Frank McDonald, Environment Editor, went back to Paris for a nostalgic visit.

It was "the shock of the new", par excellence. Not since the Eiffel Tower was completed in 1887 had Paris seen such a sensational contemporary structure as the Pompidou Centre when it first opened to the public in February 1977. Hi-tech architecture had arrived with a big bang in the City of Light.

With its ducts, pipes, tubes and shafts on the outside, hanging from the building like entrails - green for water, blue for air conditioning, yellow for electricity, red for elevators, etc - the gigantic rectangular "building as a machine" was fiercely attacked by critics as resembling a gasworks or oil refinery.

But it was an immediate success with the public. Planned to cater for 5,000 visitors a day, it was attracting five times as many to its permanent collection of contemporary art as well as its ever-changing exhibitions, a public reference library and IRCAM - a centre for acoustic music popular with younger people.

It may seem odd that the centre is named after Georges Pompidou, Charles de Gaulle's faithful lieutenant and successor as president of France. But it was his vision in 1969, in the aftermath of the student revolt in Paris the previous year, that the city should have such a cultural centre at its heart.

Long before the advent of our digital age, Pompidou declared: "It is my passionate desire that Paris have a cultural centre which is both a museum and a creative centre where the plastic arts can flourish alongside music, the cinema, books, audio-visual research, etc". Sadly, he did not live to see it realised.

An architectural competition for the project in 1970-1971 attracted 681 entries from nearly 50 countries. It was won by a young team comprising Richard Rogers along with Italian architects Renzo Piano and Gianfranco Francini, who deliberately set out to demolish the idea of an "inhibiting cultural palace".

As Piano put it, they wanted to create "an extraordinarily free relationship between art and people, set in an urban context". The site, on the Beauborg plateau directly north of Notre Dame cathedral, had been derelict for years and was used as a surface car park - once a very familiar sight in Dublin.

The building they designed is undoubtedly large - 166 metres long, 60 metres wide and 42 metres high. On eight levels, including a double basement, its glazing extends to 11,000sq m. But equally inspired was their decision to create a vast sloping piazza in front, as a homage to the Campo in Siena.

The piazza is an extraordinarily lively place, especially in summertime. Jugglers, acrobats and musicians all compete for the attention of people queuing to get into the Pompidou Centre or sitting out in the sunshine. It also flows into the adjoining Place Stravinsky, with its kinetic sculptures in a fountain.

Here too is the IRCAM building, designed by Renzo Piano and completed in 1989 as an extension to the Pompidou Centre. Its characteristic red terracotta panels were a very "new thing" at the time, but that was long before they were plastered all over new buildings around the Potsdamer Platz in Berlin and copied elsewhere.

One of the great devices in the Pompidou Centre was the cast steel "gerberette", called after the German engineer Heinrich Gerber who invented it. Designed by Irish-born Peter Rice, the gerberettes are used to support steel girders with a span of 50 metres that underpin the floor "trays" of 7,500sq m.

The central design idea was that the floors should be entirely free of structural columns, to make great clear spaces for exhibitions and other activities. It was for the same reason that all the usual services one finds inside a building were festooned on the exterior; this was not an architectural caprice.

The Pompidou Centre, including its IRCAM extension, cost a total of 933 million French francs (€142 million). Twenty years after its opening, the main building was showing so much wear and tear that it was closed for renovations. These cost almost as much (€137 million) and it re-opened on January 1st, 2000.

It is now well up there with the most visited sites in the world, attracting 150 million visitors in 30 years - more even than Notre Dame. Seven years after its renovation, however, the wear and tear is beginning to show again, with paint peeling off the lower levels or being bleached by the sun higher up.

But at the time it was built, it ushered in a new era of hi-tech architecture, including the Lloyds Building in London (1984), also designed by Richard Rogers, and numerous less well-known examples.

Its success also presaged an extraordinary period of renewal in the French capital over the past 20 years.

This has seen such cultural additions to the city as the Musée d'Orsay, the Grand Louvre, the Institut STET du Monde Arabe, the Opera Bastille, Parc La Villette, the Bibliotheque Nationale de France and, most recently, Jean Nouvel's Musée du Quai Branly, near the Eiffel Tower, dedicated to indigenous art.

The Pompidou Centre is also expanding its cultural scope, with a new branch - designed by Shigeru Ban and Jean de Gastines - due to open in Metz next year. A proposal for a branch in Singapore, designed by the ubiquitous Daniel Libeskind, did not materialise, but China is now being considered.

Meanwhile, the views from Restaurant Georges on the rooftop - run by Thierry Costes, son of celebrity French restauranteur Gilbert Costes - are as stunning as ever. And for those who can't afford it, there's still plenty to do, such as spending an afternoon in the music library, a sort of communal YouTube.

It would be impossible to imagine Paris now without the Pompidou Centre. Although the fact that it needed to be thoroughly renovated after just 20 years of use was not a great advertisement for hi-tech modernism, it is as firmly part of the city's cultural landscape as the Eiffel Tower itself.

After visiting the building, architects should make a short detour to the rue des Archives - in the direction of the Marais - where Renzo Piano maintains a model-making studio behind a plate-glass shop window. It is full of exquisitely crafted architectural models, mostly in balsa wood.