Grimshaw and Foster, however, have been allowed into the thick of things, each making highly individual and very visible contributions to what is fast becoming the centre of Europe. Grimshaw's all-new building is known locally as "the Armadillo" because it is made of a sequence of giant steel arches of varying sizes, which respond nicely to the irregular form of the site. Where you can see the real shape of the building - which is round the back - its sinuous shape, clad in scale-like stainless steel panels, is indeed armadillo-like. And even on the main street facade - where those unbending Berlin planners insisted on a flat, rectilinear glass front - the legs of the arches with their huge, claw-like cast aluminium feet are still fully exposed at pavement level. At each end, the form of the giant arches is fully expressed. You can see how the floors hang from them, instead of being supported from below as is usually the case.

Grimshaw: Ludwig Erhard Haus

Berlin is rapidly coming to regard the Armadillo with affection. Forget commerce and share dealing - it has become a party venue. The dramatic spaces inside include a vast foyer running the entire length of the building, and two spectacular atria with aluminium wall-climbing lifts like sci-fi sarcophagi. The place is at its best when it is humming with people having a good time. Before long, it will surely be used for fashion shows and film sets.

Foster's Reichstag, as befits a state parliament building with an extraordinary history, is a more sober affair, but no less dramatic. Paul Wallot's 1894 neo-Renaissance building was burned out in 1933 after the Nazis came to power, was shelled by victorious Soviet troops in 1945, was given a lacklustre 1960s makeover and was finally completely wrapped up by the artist Christo in 1995. Foster at first proposed placing a huge canopy over the entire building and its surroundings, stretching right down to the banks of the River Spree. Nice idea, Norman, but just a bit expensive: so the canopy went, and the glass dome came in.

The more modest solution reveals a particular Fosterian strength, since this is one out-and-out modernist who is often at his best when working with historic buildings. In the event, he has treated the Reichstag rather as he treated the Royal Academy in London, but on a far grander scale. So he has revealed as much of the old building as possible, and then lightly perched his own additions within it. You still see the Cyrillic charcoal graffiti of the Russian soldiers on the walls inside, for instance, and much of the damaged stonework remains visibly damaged. The circular parliamentary chamber is visible from outside through glass walls. Public galleries are cantilevered right into the centre of the space, so you can sit and observe government at work.

Foster: ceiling of Reichstag debating chamber

The space is dominated by two things: an enormous suspended German eagle (not to Foster's design, though he had a go at doing one) and an even huger mirrored hanging cone-shaped object, rising into the glass dome above. This doubles as a light-scoop and funnel for removing stale air. On the roof, there is a public restaurant to one side of the dome, whence the spiral ramps take you up to a viewing platform at the top. From here, the views of the new Berlin are stupendous.

Foster: mirror cone in Reichstag dome

The first parliamentary session in Foster's Reichstag takes place in April, though the new and refurbished government buildings behind and alongside it, together with a completely new central railway station nearby, will not be finished for some time yet. The old commercial district meanwhile has Grimshaw's Armadillo as its focus while the new commercial district around Potsdamer Platz and the adjacent Leipziger Platz will not finally be complete for around another five years. There is no doubt that Berlin is an extraordinary place - perhaps the most exciting city in Europe right now precisely because of its transformation - but maybe those Prussian planners have got a point. Perhaps Berlin needs to get boring and dour, like Bonn or Frankfurt. Otherwise, what are all the other European capitals, their power reduced within the Euro-state, going to be left with? In the end we will, I think, always have Paris.