The opening of Santiago Calatrava's magnificent new railway station in Liège earlier this month was the crowning moment in a long-overdue programme of urban renewal. If ever a city needed a makeover, it's the capital of Belgium's French-speaking Wallonia region.
Liège used to be prosperous and beautiful, but the collapse of its steel industry – and a lot of its buildings during the last days of the Second World War – put paid to all that. What damage the V1 and V2s didn't do, town planners completed in the 1960s. I remember my first sight of Liège 10 years ago. Its railway station resembled Sink Estate Central, its retail outlets would have cured the most committed shopaholic, and its hotels were the exclusive preserve of grey businessmen on very modest expenses.
Still, there were reasons to come to Liège even then. The city is rich in medieval churches, abbeys and convents. It has a fine 19th-century opera house, the first shopping arcade in the world (1831), several parks and palaces, and a lovely museum on the quayside dating from the 16th century. But you had to seek out these jewels and not be put off by monstrosities such as the Longdoz Shopping Centre, a monument to the arrogance of post-war architects and their belief that as long as a building was new and stood out like a sore thumb nothing more should be asked of it.
I knew Liège had changed as soon as my train eased into the station. The first flowing white line of a Calatrava building is instantly recognisable. The Spanish architect began his career building amazing bridges and his major works today – opera houses, airport terminals, the Ground Zero subway station – still resemble bridges. But such bridges! Strut leads to strut, a series of daring, vaulting spans, until the whole structure is revealed, a huge and perfectly symmetrical skeleton of bleached white bones topped off by a broad glass canopy. The lines of the station frame the view below like the aperture of a giant white eyelid. The only problem is what the eye is looking at.
"It's such a shame," I said to Joyce Samson, site manager for Liège TGV as I gestured to a hideous 1950s apartment block in brown ceramic brick. "It's going," she reassured me, "and the tax office behind it. Next time you come there will be a boulevard leading straight from the station to the river."
My next glimpse of the new Liège was Médiacité, which has done what no architectural critic managed and demolished the Longdoz Shopping Centre. My host was Jean-Michel Despaux, a dapper French developer in a sober suit and hard hat. His company bought up the last brown-field site in Liège, a former steel mill, with the intention of creating a media and shopping centre. "Then one day the city asked us 'Please develop the Longdoz Shopping Centre, too'. It was in the next block, a very, very nasty shopping centre. The city authorities have been the driving force behind many new initiatives. They saw that Liège occupied a great geographical position in the centre of Europe and had a lot to offer."
The deal that Despaux and the city struck was that his company would buy the road junction between the two blocks so that they could be developed as one complex. The company appointed Ron Arad, head of design at London's Royal College of Art, to create a long curving arcade with the most remarkable sinuous roof linking both buildings. Though made of steel, Arad's arcade writhes almost like a living creature. No two steel struts are the same and the entire structure – too complex to glaze – is covered in a Teflon membrane of the kind that encased the Water Cube at Beijing's Olympic park. It's mostly white but with flashes of red. The floors are similarly woven together out of white and red resin.
Arad's 360-metre-long arcade will make a difference to shopping in Liège. It is exciting and unpredictable and makes you want to see what's round the next bend. And if all goes to plan, from 21 October Liège will have the unique honour of being home to both the oldest and newest shopping arcades in the world.
My final vision of the new-look Liège answered the lack of a five-star hotel. On the Mont Saint-Martin, the Crowne Plaza group is completing a lengthy refurbishment of two small palaces, the Royal Sélys Longchamp, an Italian palazzo with two wings and a ballroom, and the more Flemish-looking Comtes de Méan, with its brick gables and defensive tower.
Again I donned a hard hat, this time in the company of Nabil Seggai, the hotel's general director. According to plans I saw, this may soon be one of the most glamorous hotels in the Low Countries, with its terraces overlooking the rooftops of Liège , its vaulted bar in the old fencing room, and its rooftop Jacuzzi suites.
But best of all is the 18th-century mirrored ballroom, currently in a state of magnificent decay reminiscent of the finale of Bladerunner. Work is slow, as new plasterwork is being cast from existing pieces and meticulously installed. I asked Nabil if the original paintwork (a dark pink with gilded highlights) would be reproduced. "Of course!" he replied. "Exactly as it was. This is why we cannot open till February."
Out on the ballroom terrace the view is spoiled more than somewhat by La Sauvenière, a huge semi-derelict 1930s Art Deco swimming pool.
"What are you going to do about that," I ask.
"Oh the city is restoring it to make it beautiful again."
Liège is changing for the better, and not before time.
How to get there
Rail Europe (0844 848 4070; raileurope.co.uk ) offers return fares to Liège from £59.
Belgian Tourist Board (020-7531 0392; belgiumtheplaceto.be ).