In Houston, for example, 6.2 miles of mostly below-grade tunnels interconnect more than 26 million square feet of enclosed space. Against such a massive reorganization of urban activity -- in effect turning the city outside in -- the centrifugal fabric of streets and sidewalks implodes.

With the elimination of traditional pedestrian activity, an alternative, centripetal city emerges as the closed, exclusive reorganization of the urban sphere. No longer a presentation to and representation of the city in the world, the center of Houston is scarcely relevant to the surrounding city.

Failing to constitute the open locus of civic identity -- what used to be called civic pride -- the imploded core has been reorganized into an elaborate, publicly subsidized office park for the region's many banking interests and oil and gas companies.