Pervious concrete has been around for twenty years or more, but its use in New Orleans is fairly recent.

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?

How can we marshal the potential of urban color while retaining a legally appropriate balance between public regulation of the private realm?

Here, from afar, is more evidence that street and square, beach and byway all have a greater and unrealized multipurpose capacity, ripe for recalibration in ever-evolving America.