The gleaming new pair of sandstone clock towers sitting on top of Dresden's central station are remarkable for several reasons. Primarily, there's the fact that they're back in something close to their original form for the first time since the city was devastated by Allied bombing in 1945. But there's also the fact that they've been rebuilt by the last architect you would associate with historical stonework in Germany - Norman Foster. Britain's global ambassador of steel and glass and all things cutting-edge is unlikely to branch much further into the field of 19th-century imitation that this, but these clock towers were a special case. Foster's team haven't just restored Dresden station, they've transformed it, and arguably improved on the original.  The clock towers are by no means the highlight of the building. It's what Foster and Partners have done with the main train shed that really takes the breath away. Rather than a conventional solid roof, a translucent skin of Teflon-coated glass fibre has been stretched over the original steel arches spanning the platforms, and the effect is striking. Arriving at the station by rail, with the winter sun low in the sky, natural light floods into the vast, curvaceous space, and every element of the three-arched structure is thrown into sharp relief; even if you had no interest in trains or architecture, you'd have to confess it's a thing of beauty, like pulling into an enormous Zeppelin.  The station was built in the 1890s, but it is difficult to believe it could be so old. You could hardly make it lighter if you were designing it today. "Every time I see it, I'm surprised at how much the colour changes as the sun works its way around the station," says Stanley Fuls, Foster and Partners' project architect. "Before, you could look up and not be able to see the roof because it was so dark. The roof they put in after the war was timber with only small plastic skylights, and the plastic had become really dull with all the diesel fumes and everything."  Now the structure's graceful curves are as clear as a diagram. There are practical benefits to Foster's roof, too. For most of the day, the station requires virtually no additional lighting, which means less architectural clutter and lower energy consumption. At night, the inside of the membrane reflects and diffuses the artificial light, creating an even wash; from the outside, it glows like a lantern. The skin is also low-maintenance: the Teflon coating, as you'd imagine, repels grime as a non-stick frying pan would. A host of other technological tricks have been deployed to make this roof work, from cable systems to cope with the build-up of snow, down to specially designed wires to keep the pigeons off (conventional spikes could damage the membrane) - but it all takes a back seat. For an architect commonly associated with conspicuous, attention-grabbing projects like skyscrapers and airports, this is Foster showing his sensitive side.  The same spirit of humility has been extended to the main station building, where the process has been one of subtraction as much as addition. In contrast to the lightweight structure of the train shed, the station itself is a monumental stone structure, whose generous arcades resemble the cruciform vaults of a cathedral. The building survived the horrific bombings of February 1945 largely intact, only to be vandalised by the East German authorities soon afterwards. But as the architects removed decades' worth of clumsy alterations, forgotten features of the station emerged. Squared-off windows throughout the station were revealed to be taller, arched ones. At the train-shed end of the station building, the original rusticated stonework and cast-iron supports for a balcony were miraculously well preserved beneath crude plaster and advertising hoardings. Two halls either side of the central corridor (originally upper and lower class waiting rooms) have been stripped back to their scarred decorative brickwork, and roofed over with unobtrusive steel and glass to create warmer, more intimate spaces.  The most conspicuous addition is a new glass cupola that rises above the front entrance, over the intersection of the two arcades. It could be taken as a reference to Foster's famous addition to the Reichstag, the new German Parliament building in Berlin, but again, it is simply a feature of the original design that has been brought back - albeit with a hi-tech twist: hovering beneath its dome is a movable transparent foil cushion. In winter it seals the heat in, but in summer it rises up half a metre, allowing warm air to flow up and out of the cupola's louvres, so the building naturally ventilates itself.  The net effect of Foster's interventions is a calm, almost monastic simplicity. The plain, pale surfaces, the minimal detailing, and the extensive use of glass all serve to create a clean, open space where before there was a dark, grimy one. The only thing spoiling it is the decor of the commercial concessions inside. "What's really great about the station is views and light," says Fuls, "and this is not our achievement, this is in the original design. If you're standing on the platforms you can see right down into the hall, or across to the other platforms. Or you can be down in Burger King and still see your train arriving up here."  The station opened earlier this month, and many Dresden residents have turned up to see it, even if they don't plan to use it yet. At any time of day, there seem to be elderly visitors standing on the new glass balcony, looking out over the platforms and their new roof. It is unlikely that they are thinking purely about the construction. Dresden will never be an ordinary city, and this station has had an extraordinary history.  During the second world war, it served as a military supply point, and saw the transit of trains full of prisoners heading for the concentration camps. After the fall of the Berlin Wall in 1989, trains carrying refugees from Czechoslovakia passed through the station en route to West Germany. Crowds watched from the platforms, then took to the streets outside to demand similar freedoms. In 2002, the city experienced its worst ever flood, and the station was a torrent of water a metre deep. Ironically, the damage caused by the floods, and the subsequent insurance payout, were what prompted the restoration of the station building.  The architects' original commission, six years ago, was for the membrane roof only. There is more to do: Foster and Partners have submitted proposals for restoring three small pavilions on the outside of the station, one of which used to be a private entrance for the King, but was later turned into a cinema.  The psychological scars of Dresden's wartime destruction have all but healed, to the extent that news of a British architect working on a local landmark barely raised an eyebrow, but you don't have to walk far beyond the station to see signs of the architectural price Dresden paid. What was once "the Florence of the Elbe", the most beautiful baroque city in Europe, is now a strange mix of rebuilt historical buildings, monolithic slabs of postwar socialist architecture, and new shopping and office blocks. The city is due to mark its 800th anniversary next year, and construction, or rather reconstruction, is accelerating. Last October, the huge, domed Frauenkirche, the protestant church that was once the city's symbol, was rededicated after a long, painstaking reconstruction, having stood in ruins for a generation. The project was financed by private and corporate donors, including many from Britain, and the golden cross on its roof was forged by the son of an RAF pilot who took part in the wartime bombing raids. Tourists now throng to see the wedding-cake interior of the church, dripping with tiers of balconies and galleries, all painted in gaudy colours and fake marbling. It is apparently a close approximation of how the building used to look, but it feels more like a three-dimensional stage set - a sad reminder of what's been lost.  A similar strategy is at play in the area around the Frauenkirche, known as the Neumarkt. Dresden's city council has pledged to accurately rebuild about 80 old townhouses and hotels in the area. Many of them have recently been finished - brand new 18th-century architecture with modern glazing and concrete structures beneath the stone cladding. Others are still fenced-off pits in the cobbled streets, containing the foundations of the buildings destroyed in the wartime firestorm.  Among those supporting the traditional reconstruction approach is Prince Charles, and British traditionalist architects such as Robert Adam and Jan Maciag have proposed baroque-style designs for the area. Others have questioned whether trying to turn back the clock to the 1920s is the best response to Dresden's situation. Some would prefer to see the ruins preserved as a memorial, and contemporary architecture built. Foster's Dresden station is removed from this debate, but it does represent a middle way that could please everyone: using current technology set against the past.  It looks deceptively simple, but Foster's project was by no means straightforward. There were intense negotiations with the client, heritage consultants, city officials and other invested parties over what to keep, what to remove and what to reinstate, hence the new stone clock towers. "There were very intensive discussions over whether Foster's should be doing this sort of thing," says Fuls. "We didn't replace stonework damaged by bullets and bombs in other parts of the building, but we thought it was the right decision here because the damage was done intentionally. Still, we wonder if it was the right thing to do. Maybe in another city we would have done something different. But it's important for many people in Dresden to have things back like they were".
Dresden's magnificent train station has been restored to its prewar glory - by a British architect. Steve Rose on the project that brought out Norman Foster's sensitive side.