Berlin will be preoccupied with its history this weekend as the city commemorates the 50th anniversary of the Air Lift, when British and American forces kept West Berlin supplied with food and other necessities throughout an 11month Soviet blockade. But these days it is a city with much to look forward to as well.

Next year the government will end its peaceful residence in the sleepy, Rhineland city of Bonn and move back to Berlin which, for all the fascination it holds in the public mind, was Germany's capital for only 74 years - from 1871 until 1945, the bleakest period in the country's history.

Berliners hope the move will mark the beginning of a glorious new age for their city. But many others fear that the move eastwards will bring nothing but trouble, reawakening old, nationalistic ghosts and unnerving Germany's neighbours.

Berlin is a city with a lot to remember and, especially in this century, much it would prefer to forget. Two world wars were planned and orchestrated here, two republics established and, for almost 30 years, a wall ran through the entire city.

Berliners got a particularly melancholy reminder of the past this week when it was announced that Conrad Schumann, the East German soldier who was famously photographed leaping over barbed wire when the Berlin Wall was being built in 1961, had hanged himself in his garden.

Ghoulish visitors to the city still make straight for a bleak expanse of rubble, earth, weeds and wire mesh just south of the Brandenburg Gate where they can pose next to a few surviving slices of the Berlin Wall which stand like brightly-painted tombstones in the middle of the wilderness.

Just beyond this mock graveyard a short stretch of the wall remains intact and energetic visitors can even climb into a concrete watchtower where East German border guards once played cards, smoked smelly Club cigarettes and took aim at their fellow citizens.

There is a fine view from here of the little green mound just to the north which marks the bunker where Hitler, Eva Braun, Joseph Goebbels, his wife and their six children died during the final days of the second World War.

This is Potsdamer Platz, once the busiest crossroads in Europe and later the barren, broken heart of Berlin, reduced to rubble by Royal Air Force bombers and then trapped in No Man's Land when the city was divided. But the minefields and dog runs have now been replaced by cranes and mechanical diggers as Potsdamer Platz becomes the largest of an estimated 2,000 building sites in Berlin.

After reunification, Sony and Daimler Benz commissioned some of the world's leading architects to create a vast complex of shops, offices, apartments, theatres, cinemas and squares.

Sony's new headquarters will be in a 100 metre tall glass building that looks so light it might soar into the air at any moment. The centre of the complex will be covered with an elliptical roof like a glass umbrella.

Berliners love to boast about the size of the building boom which has followed reunification e.g. the 1,106 architects who applied to design the new government offices at the River Spree, making it the biggest architectural competition in European history; the 75,000 flats being built in the north of the city in the biggest housing development in Germany; the 1,100-bed hotel under construction in the south-east.

Run-down areas in the east of the city have been given a face-lift and dingy, old courtyards have been transformed into smart, open-air meeting places surrounded by expensive restaurants and elegant bars.

The Hotel Adlon, one of the most fashionable addresses in the city before the Second World War, has been rebuilt next to the Brandenburg Gate. And the Unter den Linden, which was on the eastern side of the Berlin Wall, has regained its status as the central boulevard of the united city, while the Kurfuerstendamm in the west retains its place as the top shopping street.

Several large building projects are nearing completion and the countdown to the government's arrival is well under way. Yet there is an air of uncertainty about Berlin this summer as the city prepares for its new role as a 21st-century metropolis.

Optimists enthuse about the return of the "golden twenties" when Berlin was the most exciting city in Europe, home to a thriving film industry, theatre and art scene and a magnet for hundreds of artists and writers from abroad.

This was the Berlin that attracted Christopher Isherwood and W.H. Auden, a thrilling, licentious, multi-cultural melange that was swept away in 1933 when Hitler came to power.

When Micheal Mac Liammoir returned to Berlin after a 19-year interval in 1950, the city was still a mass of rubble following the bombardments of the second World War.

"Unspeakable emotion swept over me on beholding, not merely the things I had dreamed or imagined long ago but the shameful spectacle of a great city so completely abandoned to ruin and defeat. Strangest of all is that the miles and miles of desolation have an unexpectedly fantastic beauty about them, something that hovers piteously in the air above the wreckage and the wastelands," he wrote.

During the Cold War, West Berlin enjoyed a special status in the eyes of the world as the front-line city in the fight against communism. The wall was a source of great misery and much inconvenience but it gave the city an eerie charm that attracted many Germans who felt uncomfortable with the prosperous conformity of the Federal Republic.

West Berliners usually coped with the abnormality of their situation by behaving as if East Germany did not exist and most visited the east only once or twice in their lives, generally as part of a school outing. When the wall was removed and east and west reunited, initial curiosity and warmth soon gave way to sullen suspicion and mutual resentment.

Easterners and westerners now work together and share a political system. But they still prefer not to read one another's newspapers and they seldom marry each other. Nearly a decade after the fall of the wall, the psychological barrier appears to be almost as formidable as ever.

This lack of a shared identity is one reason some Berliners fear that the politicians who move up from Bonn next year will impose their own, dull stamp on the city.

More cheerful souls predict that influence will flow in the opposite direction and that the po-faced administrators from the Rhine will soak up some of the good-natured, anarchic spirit on display during Berlin's annual Love Parade.

Others suggest that, after all that Berlin has survived this century, it will not be intimidated by an invasion by bureaucrats. In the words of a sentimental song that has remained popular for almost a century:

So lang noch untern Linden

die alten Bume bluhn kann nichts uns uberwinden Berlin bleibt doch Berlin.

(As long as on Unter den Linden the old trees still blossom, nothing can overcome us, Berlin remains Berlin.)