We assume more complex human societies began living together in close proximity as a means of protection against marauding armies. It was quickly determined, though, that denser populations meant greater access to all kinds of other economic and social benefits.  The scale of cities proved that bigger, was indeed, better.  Have we reached a tipping point in the C21st – an era of megacities and world cities – where the disadvantages of huge, sprawling, land-based metropolises are starting to outweigh the advantages? 

In this discussion, scientists, economists, urban planners, futurists and technology entrepreneurs consider the future of the city and identify possible alternatives, once thought the domain of science fiction and cartoons.