Citroen's latest model isn't a car but a building. But then Number 42 Champs-Élysées, Paris, is no ordinary building; it's a showcase for the Citroen brand that uses both its architecture and the altering exhibits within to revitalise the French firm's art-nouveau image. We went along, not only for the free champagne and a trip to Paris, but because we wanted to know if the C-42 (as the new building is named) really symbolises a return to Citroen's original values.The overriding sensation within the building is of the brand's history. As you enter you are met with the sight of the C-Metisse; a concept shown at the 2006 Paris motor show that exhibits diesel-hybrid technology within a large sports-coupe body. It's a concept that points to the future of Citroen more than any other.But as you walk up the building you pass a DS, a 2CV and finally a Traction Avant. Each of these models can be credited with altering the motor industry: the DS for all its technical advances, the 2CV for mobilising the masses, and the Traction Avant as the first mass-produced front-wheel-drive car. And this within a building that boasts a glass façade made up of Citroen chevrons, encased within wrap-around iron bands; all created using the most modern building techniques on a site where a Citroen building first existed in 1927.You can't buy cars in the C-42. You can only marvel at what Manuelle Gautran, the building's architect, has achieved, and consider what Citroen means by opening such a modern building on such a traditional avenue of Paris.The most exciting thing is that everything from the mad press conference (where three men painted an image of the C-42 on the wall behind the speaker), to the iconic lines of the Traction Avant inside an angular glass building suggests that Citroen really is returning to its avant-garde roots.Citroen needs this to keep a separate identity from Peugeot (which is part of the same PSA group), and to maintain its unique image. And if concepts such as the C-Metisse and more recently the C5 Airscape are anything to go by, the company is working to make that happen.The C-42 building aims to inspire and innovate, and it has succeeded. To transfer that same achievement to a modern car will not be easy, but the expertise needed to do it is there. Time will tell, but maybe, just maybe, Citroen is back.