the bridge open for a boat to move out from the canal and into the harbour beyond
To be mundane, I suppose Cirkelbroen is simply a bridge over a canal, where there had been no bridge before, but it means that, for the first time, people on bicycles or walking can get along the waterfront of the harbour between Knippelsbro - the historic bridge at the centre of the harbour that links the historic centre and Christianshavn - and Langebro - the main traffic bridge between the city centre and Amager. All that was needed was a simple steel bridge that could either be raised or swung open to let boats from the canal sail out into the harbour.
Of course the bridge designed by Olafur Elliasson is so much more than it … but even so … in the end … it all has to work and it has to be robust and it has to be relatively quick to move and and easy to operate. So that it is the engineering part of the design that allowed the concept to be realised.