As a whole group, you are going to construct one invented city, with each group working on a city plot with a series of chain reactions within it. All of these plot will fall under a general theme. Together, discuss possible themes and decide on one to work within.
Example themes might look like the ones we used for sketching prompts in this exercise (Plant City, Alphabet City, Pet Metropolis). They should be general enough that each group has creative freedom, but narrow enough that in the end all of the plots will come together to look like one cohesive cityscape.