Nivola sees it even before he enters the city. As his airliner descends toward Orly International Airport, he sees not the sprawling, sterile suburbs found on the outskirts of many cities, but farms, scores of them.

The farms are there in defiance of the pressure of development because the French government subsidizes the farmers and makes it profitable for them to continue farming.

"That's one of the reasons Paris is such a great place," Nivola says. "French farmers are heavily subsidized by the government, so they don't easily sell off their land to developers. Of course, taxpayers and consumers pay high prices for those subsidies, but it also means less encroachment on the farmland."

Supporting farmers is just one of a number of French policies that make Paris a city in the best sense of the word.

Another is what Nivola calls "the rigorous effort to clean the city and maintain the parks. The budget for these things is enormous compared to the typical American city. And they have many times more police wandering around making sure people don't vandalize the city."

Paris employs a huge work force to keep the city clean and its use of golf cart-like vehicles to vacuum dog droppings has received admiring -- and sometimes wry -- attention in the international media.

Paris also derives charm and intimacy from the small shops that populate its neighborhoods. This, too, is no accident.

"Bakeries, a fish store, a butcher, a grocery store, conveniences like that are at your fingertips," marvels Nivola, "all within a half a block or so.

"With the exception of parts of Manhattan, there is nothing like that in the United States. It's unheard of, and it's because the French tend to protect small businesses. They make it harder to knock down buildings and put in big-box retailers."

The distinction is further emphasized by the limits the French government puts on business hours, a curb on individual liberty almost unheard of in the United States.

"They are much more regulated and protectionist," Nivola says. "The downside is that it means the cost to consumers is probably somewhat higher, but the convenience of small shops is part of the vibrancy and charm of these neighborhoods."

Another significant difference is that in France, commercial and residential areas are not nearly as segregated as they are in the United States.

"Cities like Washington have vast neighborhoods that are like suburbs," Nivola says. "For example, northwest Washington is like suburbs such as Bethesda, Maryland, or McLean, Virginia. It's very residential, with just a few little pockets of commercial activity. But you can only reach them by car, so you might as well live in the suburbs."

Also, residential patterns are reversed. In Paris, the well-to-do tend to live in the center of the city and the poor on the periphery. The opposite is true in the United States, where the poor often live in old, decaying neighborhoods, which raises another issue.

Preserving historic buildings in Paris is relatively easy, since they are generally in continuous use and upgraded rather than allowed to fall into disrepair. But the flight to American suburbs has left once-beautiful homes and buildings in the hands of the poor who lack the resources to renovate them.

"It always surprises me how often old buildings get knocked down in this country and a new structure goes up," Nivola says. "The architecture is very diverse, but a lot of it is junk."

That "junk" includes things like convention centers, sports arenas and vast parking lots, "facilities that are not residential or where people live," Nivola says. And where there are areas without people, "you no longer have cities that are dense and vibrant as they should be."

Finally, there is the issue of transportation. It is expensive to own and operate an automobile in France, as it is in other parts of Europe. In the United States, however, cars are inexpensive, gasoline is cheap and land is seemingly inexhaustible.

Europeans and people in many other parts of the world live in smaller, tighter confines than Americans, and their sense of community is often defined by boundaries established long ago.

Downtown areas are sometimes closed to vehicles, leaving pleasant pedestrian-friendly streetscapes amidst historic buildings, sidewalk cafes and other amenities.

Compare that, says Nivola, with places such as Phoenix, Arizona, a city urbanizing faster than almost any other in the United States.

"If you extrapolate its rate of development in the next few decades," Nivola says, "you would still find that in 2020 less than 2 percent of the surface area of Arizona would be urbanized. That's how much space we have to spare in this country.

"So it's natural for Americans to be lavish in this country in the use of land, and in a way it makes sense. You use the resources you have."

Since the poor areas are on the fringes of the city, space is at a premium in Paris, something Parisians are accustomed to but others sometimes are not.

"Europeans are accustomed to tighter housing and making more use of public space," says Nivola. "They often meet in cafes instead of living rooms or yards. But I have French friends who say that Americans who live in Paris don't seem as comfortable in crowded little bistros and cafes as the French are."

There are other factors -- high taxes, a sluggish economy, the difficulty in getting a mortgage, high energy costs -- that explain why Paris is developing differently than Phoenix.

But neither is immune to the pressures of urbanization.

"Things are changing all over," says Nivola. "Sprawl and rapacious development are happening all over Europe, and the developing world."

Following are anecdotes about the problems urbanization has caused cities in various parts of the world.