If the 20th century city was marked by forces that pulled cities part, resulting in a discrete environment of partially autonomous units, the successful 21st century city is marked by a return to complementary interaction of a fully-functioning whole. Aided by advances in industrial areas that are relatively clean and good neighbors, and a shift toward a knowledge economy that prizes synergy and face-to-face interaction, the city as being central is a fundamental concept.
While theorists were right to describe the transition to a regional model in the 1940s and 1950s, their prescription was flawed. Instead of focusing solely on the area of regional focus (like a downtown), the constituent neighborhoods must be thought of as the essential flesh of the system, without whom the whole region would die. Because while areas of regional focus were becoming relatively more important in this system, this did not render neighborhoods obsolete.