From the detached house through the attached row house, townhouse, crescent, or atrium house to the urban tenement, the apartment block, and finally (with the advent of elevators) the high-rise tower, habitation in the city has responded to increasing demands for concentration. As the forms of our public realm and places of work have changed along with forms of technology and society -- so too has evolved the third major element of all cities: the place of residence.
Although relatively recent in historical terms, the high-rise apartment structure has become the almost universal response to housing in cities today. To be sure, vast amounts of relatively low-rise housing continue to be built in expanded regional cities -- from single-family tract homes in North America to densely packed favelas and barrios in the Third World. But increasingly, in the centers and at the perimeters of cities, for the poor, middle-income, and affluent, the high-rise, elevator- dependent apartment building emerges worldwide as the predominant urban home.
Two economically diverse markets have influenced both the location and the design of residential towers: mass public housing and market-sensitive, "luxury" housing. The images for mass