A modern city has two diametrically opposed functions. It must provide services to the citizen, i.e., grocery and other stores, medical services, libraries, transportation and communication services, and entertainment, to name a few; and the city must serve as an import-export center for information, money, goods, and materials. The distribution of goods and services that are consumed by the residents of the city is necessary to support the life of the citizen, but these activities often conflict with the import-export function of the city. Moreover, these activities do not always relate to the life of the citizens directly and in most cases are segregated from them into business and industrial areas.

Among the problems of the city is the construction of viable human communities that satisfy the material and aesthetic requirements of man while maintaining compatibility with the technical, business, and industrial demands of the city.

Modern metropolitan areas are networks of communication and transportation—an interwoven network of the transportation of people and things and the communication of information and ideas. The water, sewer, electric, and telephone lines are obvious parts of this network, as are the streets, roads, and highways. At the intersections of the network, most cities have developed enclaves of specialized activities such as shopping districts, restaurants, theaters, parks, schools, libraries, business and manufacturing areas, and along the transportation corridors, particularly at crossroads, the city is in a continual state of change and growth.

Modern architectural concepts of the city as an assembly of plug-in modules derive from the notion of the city as a network. Units for the plug-in city are conceived as mass produced, easily assembled sections that can be adapted for occupation as business or industrial premises or as living quarters. Since all of the elements would be module in construction, all that is necessary is for the unit to be plugged into the facilities and energy sources appropriate to the function it is to perform. Although the plug-in city has not developed beyond the drawing board, its proponents claim that it would allow for great diversity in design by using marketing methods similar to those in the automobile and clothing industries where style and design, coupled with random geographical distribution, produces diversity without affecting basic function.

The various areas of today's cities, however, are not accessible without the aid of transportation; the distances are considerable and for most people the energy and time required to walk can be more profitably used in other pursuits. The mix of residential neighborhoods, business and industrial districts, and recreational areas that comprise a modern city must function as an integrated whole if the city is to prosper. The concept of the walking city relates to the scale-size of its components and the relationship of this scale-size to man, and its effects upon man the biological organism. If our future cities are to be livable, greater emphasis will have to be placed on establishing a viable biological community in those areas where people spend most of their time.

The size of the components of the walking city is determined to some extent by the physical capabilities of man, i.e., the velocity and ease of human locomotion and the energy required to perform certain essential tasks. In addition, each component of the city must enjoy a high degree of self-sufficiency. In the ideal walking city, the goods and services essential to everyday life will be conveniently located where people live and work, requiring only a modest investment in time and energy in order to procure them. Walking within the neighborhoods and districts of the city is a perfectly feasible undertaking for most people and, in an age when overweight is a major physiological problem, enormous health benefits would be derived from the development of walking cities. Dr. Jean Mayer, a world authority on obesity and energy metabolism, has said that inactivity is one of the most important causes of overweight because our bodies' regulation of food intake is not designed for the mechanized, sedentary conditions of modern life. Thus, the development of walking cities would not only re-establish man in harmony with his environment, but would contribute to his physical fitness.

The size of the walking city can vary widely, spreading over hundreds or thousands of acres, or it can be a megastructure or any combination of low density-high density areas. The essential feature of the walking city is that it be a complete human ecological community capable of providing the services necessary to sustain itself, as well as providing for the comfort, well-being, and security of those who live there.

A megastructure, that is to say a single structure occupying perhaps a square mile of territory and rising a mile into the air, is a mind-boggling concept. But ecologically the principles that apply are comparable to those for the city spread over thousands of acres and built according to conventional standards. A well-designed megastructure includes places where people live as well as where they work and play. These components, if they are to contribute to the integrated whole of the city, must be accessible to each other by transportation scale-sized to humans—for example, by escalator or elevator. The important consideration is that those portions of the community with which man has to interact must be size-related to him because he can only interact with his immediate surroundings, not with the total city. Therefore, although the city can have any number of components and attain enormous size, each component must be scaled to human size.

The technology of megastructures is not a future dream but already exists; for example, the World Trade Center in New York City. The flaw in the World Trade Center is that it is a concentration of business activities without the concomitant residential communities. As a result, there is an influx and outflow of people, with an enormous number of people using the building during the daylight hours and at night its use falls to a low level. The entire Wall Street area of New York City and comparable business districts in most modern cities experience a similar fate. These areas are viable human communities only between 8:00 a.m. and 5:00 p.m., when the Nation's business is conducted and local retail business flourishes. For the rest of the time the streets of these areas are deserted and dangerous.

The shift from the single-purpose function of suburbia or a World Trade Center or a city of thousands of acres to communities of business, industry, and residences will require reintroducing into the city some of the elements that existed in most of the world's cities before the advent of the automobile. Since the advent of the automobile, the city has been slowly transformed to accommodate it, and because of its energy, speed, and distance capabilities, the car has distorted the man-city relationship. Suburban expansion preceded the automobile and was made possible largely through the development of mass transit trains, but the areas around the transit terminals usually remained scale-size. The areas around the city's mass transit terminals accommodated and still accommodate persons on foot or with yet other public transportation. The areas around mass transit terminals in the pre-automatic crush were also served by local public transportation and usually serviced towns and villages that were quite compact by today's standards.

The automobile provided man with an overwhelming sense of power and independence and accelerated the development of dormitory suburbs. As the latter grew, so did man's dependence upon the automobile, for suburbia provided little in the way of work or recreational and cultural diversions, thus making mobility essential in order to participate in these activities.

In his study of the city of Detroit, C.A. Doxiadis concluded that every resident of Detroit needs a car because a person with a car has 20 times as many social contacts and opportunities to make a living or to exercise free choice in purchasing or entertainment as a person without a car. The only solution to man's dependence on the automobile lies in an adequate public transportation system, but even then the one man-one car regimen will be hard to break.

Frank Lloyd Wright's approach to establishing man in harmony with his environment was to construct houses that were as much a part of the landscape as possible. His ideal city was a rural setting of open spaces and widely separated dwellings. Business and industry were located at a distance. Broadacres, as his plan was called, more aptly describes the ultimate suburbia, with individual dwellings isolated on substantial plots making it impossible for the whole to form a viable human community.

The ideal habitat for man is not necessarily that which blends aesthetically with the landscape; it is that which satisfies man's organic as well as his psychic requirements. The concept of home as a habitat should not begin with a decision about the number of rooms or the amount of rent or even how much open space is associated with any given dwelling. The paramount need in a human habitat centers on the physical and biological surroundings that generate a feeling of security, comfort, and well being. Obviously, our surroundings must be conducive to functioning efficiently and the decor and furnishings must please our artistic sense, but without the basic survival requirements built in from the beginning, no collection of buildings, whatever their artistic merit, by themselves constitute a viable human community.

The single most essential element that a community must provide for its members is security. People living in tribal societies often live in dwellings that provide little other than privacy, yet they are secure if the community is secure. The wall paintings in the caves of the Dordogne region of France and elsewhere were created after the fact of the security and comfort of the cave. A cave was not only a place to find protection from the elements; the physical construction of a cave permitted it to be defended with a minimum of force, and this alone justified its utility as a dwelling for man. The analogy of a modern apartment to a cave is complete down to the single opening (the front door) being its strongest defense feature.

If a dwelling is to provide security to its occupants, it must be in a community that engenders security, both within the domain and in the community beyond. The Treetop Hotel of South Africa's Kruger National Zoological Park probably meets most of the requirements for good housing and provides security for the residents as long as they stay within the habitat, but the surrounding community remains hostile. If each man's home must meet the physical requirements of a fortress, no community is possible; for only in the collective ecological properties of communities is security attainable, and only after the requirement of security is satisfied can comfort and well-being be attained. Schools, libraries, art galleries, symphony halls, universities, amusement parks, baseball and football stadiums, and all the other paraphernalia of modern life are irrelevant in environments not habitable by man, and it is security that makes habitation possible. Comfort and well being make a secure environment livable and provide the millieu for the amenities.