Cities are just a physical manifestation of your interactions, our interactions, and the clustering and grouping of individuals.

Cities are the crucible of civilization.

Exciting cities stay exciting, and boring cities stay boring.

Cities tolerate crazy people. Companies don't.

Cities are obvious metaphors for life. We call roads 'arteries' and so forth.

We form cities in order to enhance interaction, to facilitate growth, wealth creation, ideas, innovation, but in so doing, we create, from a physicist's viewpoint, entropy.