By looking at our assets holistically, we can create a fully integrated, intelligent approach to the greening of cities, one that combines carbon savings with an increased quality of life.

If our cities must be dense to be competitive and sustainable, we must also look with care to the potential displacement of uses, institutions or traditions -- not to mention the artifacts we will leave behind.

More so than public squares -- which require a conscious set-aside of assembled space -- corners naturally result from crossroads, the elemental feature of travel between places.

Cities are hubs of human interaction, and the urban experience can be enhanced by authentic participation in the dynamics of a place and transitions to nearby venues.

What if American cities legislated brighter color amid windows, balconies planted green and encouraged flags and hanging laundry? What if homeowner associations and rental contracts required vegetation and decoration?

Once a big idea is vetted -- whether in an authoritarian or democratic way -- what assures its success? Most particularly, what if, from Day One, the vision pushes comfort zones of the achievable; politically, legally or monetarily?