It is one of the most ambitious construction projects in Europe yet it is fast turning into a worrisome political obstacle that threatens to hasten the demise of Chancellor Angela Merkel's ailing coalition. Sixteen thousand demonstrators turned out to protest against it at the weekend, death threats have been issued against its promoters and the building site at the centre of the scheme, in the middle of downtown Stuttgart, is policed round the clock to guard against saboteurs.
The deepening row is about a hotly disputed plan to completely rebuild Stuttgart's main station at the staggering cost of €7bn (£5.8bn). The hugely ambitious scheme involves bulldozing most of an early 20th century railway terminal acclaimed as a monument to early Modernism. It will be replaced by a mammoth underground station that will turn one of Germany's least attractive provincial capitals into an international rail hub.
Christoph Ingenhoven, the chief architect behind the scheme dubbed "Stuttgart 21", is adamant that his project will put the south-western provincial capital on a critical rail crossroads at the centre of Europe. "As an architectural statement, it will have the force to redefine the future of Stuttgart," he claims.
However, the project's growing array of critics argue that the scheme is the sort of grandiose and financially bloated undertaking that belongs to an earlier and greedier pre-crisis era. They claim that a mega project cannot be justified in a Germany currently suffering €80bn-worth of public spending cuts. They say it will rid the city of its prized Paul Bonatz designed Modernist station building and with huge state-owned concerns like Germany's main rail operator Deutsche Bahn at its centre, they claim the development smacks of the kind of cronyism that has become the hallmark of countries like Silvio Berlusconi's Italy. "There is simply the feeling that something is deeply wrong about this project," says the actor Walter Sittler, who is one of the leaders of the stop-Stuttgart 21 campaign, "It is a bottomless pit. Its value will be minimal but the destruction it will cause will be immense."
Yet by any standards the scale of the Stuttgart 21 scheme is breathtaking and not only in terms of cost. Stuttgart's current station is a dead end. Trains that arrive have to shunt backwards to leave. Stuttgart 21 will end the inconvenience by swinging all of the station's rails through a 90 degree arc and turning what is now a terminus into a vast underground railway station which high-speed trains will simply pass through on their way eastwards from Paris to Vienna or southwards from Hamburg to Rome. Pierced by deep eye-shaped light wells, the new subterranean terminal will also give Stuttgart a direct rail link to the city's airport taking eight minutes, cutting 20 minutes off the current rail connection to the airport.
Yet achieving such ambitious transport goals in Stuttgart – a city renowned for its hills and serpentine-like access roads – will not be easy. The Stuttgart 21 team plans to do it by blasting a total of 26 tunnels into the hillsides, laying some 70 miles of new over and underground railway line and constructing dozens of new rail and road bridges throughout the region. Architect Mr Ingenhoven says that by putting Stuttgart's main railway station underground, the city will be "handed back" a new recreational green space right in its centre.
Mr Ingehoven and his team, Stefan Mappus the region's conservative Christian Democrat Prime Minister and Deutsche Bahn chief Rudiger Grube all point out that Stuttgart 21 – a scheme first put forward in the 1980s – has been subject to years of public consultation and seen off dozens of attempts to get it stopped in the courts. "People have got to accept this and allow work to begin," says Mr Ingenhoven.
Yet ranged against the promoters is a growing, vociferous and militant protest movement which embraces ordinary city folk, disaffected architects, conservationists, women's groups, leftists, breakaway Social Democrats and perhaps most significantly, the region's increasingly powerful Green party.
Opinion polls show that 58 per cent of Stuttgart's population is opposed to the project. Last week, as the station site was fenced in preparation for building, the stop Stuttgart 21 campaign began the first of a series of protests aimed at halting the project.
For the architects and conservationists among the protesters, the demolition of the prized Bonatz station is another humiliation for a city that was badly damaged by Royal Air Force bombing in 1944 and then mutilated by post-war planners intent on building a "car friendly city of the future". Writing in The New York Times, the architectural critic Nicolai Ouroussoff described the Stuttgart station as Bonatz's "most masterly balancing act" and as being "as haunting as an early De Chirico painting". The plans to demolish most of the station left the city's planners open to charges of "facadism" – the practice of bulldozing everything but a few relics of an architectural gem, he claimed.
But for many people it is the sheer cost of the project that is so off-putting. Initially earmarked at €2.6bn, the total price currently stands at almost €7bn and is likely to rise even higher by the projected completion date in 2021. The disruption it will cause in the city will also be considerable: "It is going to be the biggest building site in Europe and it will last for 10 years," complained one angry protester to Germany's SWF television channel. The protesters want Stuttgart 21 scrapped and replaced with a more modest project that will retain all of Bonatz's original station.
For Ms Merkel however, the most troubling aspect is that it is vehemently opposed by the Greens. Cem Ozdemir, the party's ethnic Turkish leader, has promised his party will do all it can to stop Stuttgart 21.
The Greens are making sweeping gains in the region as a result and have upped their vote share to an impressive 20 per cent over the last 12 months. The party is now on course to oust the region's ruling conservative-liberal coalition in key state elections next March by forming a coalition with the Social Democrats. Such an outcome would be a disaster for Ms Merkel. It would not only mean her party's defeat in one of Germany's strongest conservative bastions. It would signal the beginning of the end of her coalition in Berlin. Opinion polls have already given the Greens and the Social Democrats combined a clear majority at national level.Reuse content