What If the Entire World Lived in 1 City?

It's difficult to think about global urbanization at the scale of individual cities. There’s no such thing as the model metropolis that mirrors the development patterns and sustainability problems of urban areas everywhere. Isolating any one city is impractical anyway; they now increasingly spread into and impact one another, blurring the boundaries between urban and rural, between developed and natural land, between metros, megalopolises and mega-regions. And then there is the simple problem of definitions: "What’s considered ‘dense’ in Australia," says Yale School of Architecture critic Joyce Hsiang, "is rural in China."

How then do we begin to think about the consequences of worldwide urbanization, what Hsiang calls "the greatest design challenge we’re faced with"?