Every few decades Berlin shrugs off the past and reinvents itself

Soon it became a joke that there was no such creature as a born Berliner. And so it has continued

EVERY so often, Berlin abolishes itself. The cycle varies a bit, but seems to average out at around 40 years - slightly longer than a generation. Then something like an earthquake happens, and the city becomes unrecognisable.

Last week, I spent a happy day in Berlin. This is a place I used to live and work in, where some of my ancestors lived and worked a century-and- a-half ago. Getting up at daybreak, before six, I walked and walked in that marvellous dry air which never lets you feel tired, hung-over or bilious; the choice of moods is reduced to mad euphoria or suicidal frenzy. The morning sky was a cloudless pale blue; the puddles were frozen hard. And time and again, in parts of the city I used to know so well, I got lost.

It is earthquake time again in Berlin. Or, to let more metaphors out of the cage, the scenery is being frantically changed for the next act, and the kaleidoscope has been violently jogged by the elbow of history. I stood on the sandy, rubbly mound in the middle of a wasteland which is all that is left of Hitler's bunker. Nobody could stand there in the old days; it was in an East Berlin death zone, stranded among the rear defence works of the Wall as it crossed the Leipziger Strasse. But where had the Wall been? And could that chaos of building sites and cranes be the Potsdamer Platz? All those smart new apartments - wasn't that where the old Nazi Propaganda Ministry used to be, and the East German "House of Peoples' Friendship"?

This is what the city does to itself. Two hundred years ago, it was a little Prussian town among the Havel lakes. Then its population doubled and, in the last few years of the 19th century, doubled again, and suddenly dear little neo-classical Berlin was replaced by a roaring, pompous metropolis with cathedrals and universities, power stations and engineering factories, sprawling out across the sandy pine-woods of the Brandenburg plain.

This second Berlin endured until 1945, when it in turn collapsed under British bombing and Soviet artillery and was swept away. In the 1960s I used to meet stupefied returnees who still had a vision of that legendary pre-war city of Isherwood and Fritz Lang and the Red Front and the Reichstag Fire - but could not even find their way to the square where they used to live.

And now it is happening again. The double city, with its broad and strangely quiet streets, its indescribably devious bureaucracies which divided people more effectively than wire and concrete, has been ploughed down by the bulldozers. This new Berlin is already the biggest building site in Europe; in the first years of the 21st century, it will be the continent's most powerful city. It will be the formal capital of Germany, with its 80 million people, but the informal capital of the European Union (Brussels a mere Washington to its Chicago or New York). Berlin will be the magnet for everyone with dreams between the Atlantic and the Urals.

Old Berliners will recognise nothing when they come back in a decade from now. And in some ways they will be proud to find that their city has raced so far away from them. This Phoenix-power is what Berlin has always been about. It is not that Berlin has no history, although that history is a short one. It is that the physical past has never been a constriction on the city's energy. In the central Mitte quarter, which lay in East Berlin, almost every building erected between about 1870 and 1980 is being demolished or is already a hole in the ground. A few are spared: the Brecht theatre on the Schiffbauerdamm, the Admiral's Palace with its decorated faade. But the rest - shabby, unloved but capable of splendour if any developer slowed down to contemplate a restoration - are doomed.

It has something to do with geography. The city lies in a barren, thinly populated plain with apparently endless room to expand. Urban planning, under the German emperors and then Hitler and then the Communists, has been more a matter of signing decrees than of creeping through myriad inquiries into compulsory purchase and environmental damage. (In old Berlin, the "nimby" could expect to be jailed, conscripted into a penal battalion or locked up in a Prussian lunatic asylum.) But geography, in the end, has mattered less than Berlin's attitude to immigrants.

This is an open city. It was open, really, even when it tried not to be. In 1743 a young man named Moses Mendelsohn came to Berlin from Dessau in order to live there beside his chosen teacher. As a Jew without a special permit, he found the gates closed against him. But he walked round the walls, which ran much where the recent Wall ran across the Potsdamer Platz and Unter den Linden, until he found a door to slip through. Mendelsohn became the father-figure of the Berlin Enlightenment, an early token that everything worth having in that city would be brought there by incomers, refugees and moonlighters.

The first immigrants were French Huguenot refugees, welcomed by the Prussian kings for their industrial skills. Then, in the 19th century, came families seeking work from eastern Germany - above all from Silesia. More streams of incomers arrived - Jews from the Rhineland and Bavaria, eastern Jews fleeing from tsarist pogroms, Poles from districts annexed to Prussia, farm labourers fleeing from the severities of Prussian estates. Soon it became a joke that there was no such creature as a born Berliner.

And it has gone on ever since. In the 1950s, West Berlin took in tens of thousands of East German refugees, and after the Wall was built in 1961, the biggest single influx of Turkish immigrant workers. The united city, with a population of 3.5 million, contains 410,000 "foreigners" of whom 180,000 are Turks. The eastern part of Berlin still has a large Vietnamese minority, brought in as cheap labour by the Communist regime. And these figures say nothing about illegal immigration and moonlighting. No fewer than 200,000 cars from Poland visit Berlin every day. These Poles are not tourists, but commuters to Berlin's enormous "grey" labour market. Many of them will eventually become new Berliners, like the Russians and Ukrainians and Romanians and Slovaks approaching behind them.

This is a success story, on balance. The wave of xenophobic violence that swept Germany a few years ago has diminished, thanks to better police work and the backlash in public opinion against skinhead nationalism. The entry rules are stricter, especially on asylum seekers, but - like Moses Mendelsohn - most of those who are determined to become Berliners will find their way in eventually. Barbara Johns, Berlin's commissioner for foreigners, said last week: "I would like to raise a monument to the fact that great cities are what they are because of immigrants."

In London, the papers announce government plans to curtail further the rights of applicants for asylum. Germany has done that, too, but against a very different background: more than a million applications in 1993, as against a mere 22,400 in the United Kingdom. Berlin's gate is still half open to immigration, while London's is tightly closed.

My grandchildren will know Berlin as a raw, fast-moving metropolis whose peoples will be as much Slav and Asian as German. Its towers will be superhuman in scale and subhuman in vulgarity. It will be fun, a place where every waking moment counts. And then, one day, it will grow tired of itself and call in the wreckers and scene-shifters, and turn into somewhere entirely different.