But in the first decade of the 21st century, urban life is changing. Cities are less frequently where people stay to lead the good life, and more often way stations for people in pursuit of it. “Cities are now junctions in the flows of people, information, finance and freight,” says Nigel Harris, a professor of development planning. “They’re less and less places where people live and work.” The coming enlargement of the European Union will give residents of up to 13 new member nations freedom of movement within its borders. At the same time, an additional 13.5 million immigrants a year will be needed in the EU just to keep a stable ratio between workers and pensioners over the next half century. All this mobility will make Europe’s cities nodes of nomadism, linked to each other by high-speed trains and cheap airline flights. Urban designers, with a freshly pricked interest in transience rather than stasis, are even now dreaming up city-scapes that focus on flows of people and fungible uses for buildings.

The bustle around airports and train stations will make the crowds in Europe’s great piazzas look thin by comparison. New city networks will spring up, following transport lines, not old national ties. In the 1990s the Eurostar brought Lon-don closer to Paris than it was to Liverpool. By 2010, routes like the PBKAL (Paris, Brussels, Cologne/Frankfurt, Amsterdam, London) line will have redesigned the map of Europe even further. Meanwhile, urban sprawl is stretching daily commutes: whereas the average European traveled 17 kilometers a day in 1970 to get to and from work, he traveled 35 kilometers a day in 1998. During the late 1990s, flush dot-comers grew used to flying from London to Paris for the day. If trade-liberalization trends continue, it won’t just be global elites who country-hop for work. In a phenomenon Harris has called “extreme commuting,” cities like London could be flying in planeloads of, say, Moroccans or Turks in weekly rotations to clean streets or hospitals.

In the 20th century, business travelers often avoided the hotel near the railway station, so often associated with grimy red-light districts and cheap pensions. But with so much traveling going on, railway stations and airports will become strong civic hubs, attracting shops, offices and restaurants. Notes Harris: “Once you’ve got an international transportation terminal, these city areas become international centers, with all kinds of activities, most often based on knowledge industries.”

Other public spaces are due for a revamp as well. Earlier architects conceived of train stations as single buildings; today’s designers are thinking of them as transit zones that link to the city around them, pouring travelers into bus stations and surrounding shops. In Amsterdam, urban planner Ben van Berkel, codirector of the design firm UN Studio, has developed what he calls Deep Planning Strategy, which inverts the traditional “top down” approach: the creation of a space comes before the flow of people through it. With 3-D modeling and animation, he’s able to look at how different population groups use public spaces at different times of the day. He uses the data to design spaces that accommodate mobs at rush hour and sparser crowds at other times. “A city is like a waterbed,” says van Berkel. “If you put pressure on one part, it will affect other parts. You can’t just build something in isolation.”

The growing mobility of Europe has inspired a debate about the look and feel of urban sprawl. “Up until now, all our cultural heritage has been concentrated in the city center,” notes Prof. Heinrich Mding of the German Institute of Urban Affairs. “But we’ve got to imagine how it’s possible to have joyful vibrancy in these [outlying] parts, so that they’re not just about garages, highways and gasoline tanks.” The designs for new buildings are also changing to anticipate the emerging city as a way station. “Architecture has classically been fixed,” says Alejandro Zaera Polo of the London-based firm Foreign Office Architects, who with his partner, Farshid Moussavi, is representing Britain at the Venice Architecture Biennale this month. “Buildings have been seen as disconnecting, isolating, defining. But increasingly, the quality of space that’s in demand is movement.”

In the Japanese city of Yokohama, for example, Foreign Office created a port terminal that incorporates the idea of mobility into the structure itself. Partitions for the space move on wheels, and there are no stairs: passengers move around on ramps. In the Dutch city of Groningen the firm created the Blue Moon aparthotel. Among the building’s “skins”: a “duvet facade,” allowing the inhabitants to zip or unzip the cloth walls, creating rooms and windows of varying sizes, depending on whether they’re using the space to sleep or for business meetings. Foreign Office is building a sports park in Barcelona that takes the notion of flexibility even further. The park will have stadiums embedded in the landscape, near playing fields, with roofs that can roll back to open the stadiums for concerts or games.

In the industrial era, cities needed to have access to raw materials to thrive. Now the trend is reversing: to attract people with the brains or capital to produce economic growth, a city has to lure them with its lifestyle and culture. In a globalized economy, spectacular parks, museums or stadiums are becoming ever more important. “In the old days, ‘hard’ locational factors, like whether you had a harbor or a traffic crossroads, determined whether you’d succeed as a city,” says Mding. “These days, attractions of the natural and cultural environment are going to determine where firms are located.” Cities may have changed since Aristotle’s time. The quest for the good life hasn’t.