FRIENDLY OLD GIRL:

Radical and far-reaching, the scheme dared to rethink the very infrastructure underpinning the city. There's still not a climate project anywhere else in the world that comes close.

And, so far, it's working. CO2 emissions have been reduced by 42% since 2005, and while challenges around mobility and energy consumption remain (new technologies such as better batteries and carbon capture are being implemented), the city says it is on track to achieve its ultimate goal.

More significant still is that Copenhagen has achieved this while continuing to grow in traditional economic terms. Even as some commentators insist that nothing short of a total rethink of free-market economics and corporate structures is required to stave off global catastrophe, the Danish capital's carbon transformation has happened alongside a 25% growth in its economy over two decades. Copenhagen's experience will be a model for other world cities.

The sentiment that lies behind Arc's conception as a multi-use public good - "hedonistic sustainability" - is echoed by Bo Asmus Kjeldgaard, former mayor of Copenhagen for the environment and the man originally tasked, back in 2010, with making the plan a reality.

Tweet   @brothersjudd