This is the first story in a new series called Dream City, which will explore the way we're designing our cities of the future, cities in which we want to live, right now. Two more stories will follow this week. Tomorrow, we'll examine the way cities are growing with creative use of their waterfronts. And on Tuesday, we'll look at the growing trend of removing freeways from downtown to create new pedestrian spaces.

New York has turned large swaths of Broadway over to bikes, benches and cafes. Los Angeles is going all-in on a plan to turn its car-addicted populace into rail commuters. And Minneapolis, the frostiest city of the Frost Belt, is creating a sophisticated citywide bike trail system that has made it the No. 1 city in the country for bicycling.

America's urban reboot is in full swing. The awe-inspiring mega-projects -- the High Lines and the Subways to the Sea -- are being held up as a sign that cities are back. But look at the crowded roster of schemes being hatched below the radar, and it's easy to believe that the new era is just now getting started. New Orleans is plotting to tear down an elevated expressway and replace it with a tree-lined boulevard that would reunite two historic neighborhoods isolated for half a century. In Brooklyn, a brand-new 15,000-square-foot rooftop farm is expected to produce 100 tons of greens for the city every year. San Francisco is planting electronic sensors in parking spaces that could eventually guide drivers toward empty spots. Streetcars are being resurrected from Tucson to Washington. Bike-share systems are going viral.

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The gleeful sense of aspiration coursing through cities today is more than mere "urban renewal." The very assumptions about what makes a city a city are being challenged. We're in a period of spectacular innovation and a dizzying demographic shift that 50 years from now might make the great migration to the suburbs look minor by comparison. Time was, and not that long ago, crime was swallowing cities whole. Today you can sleep in Zuccotti Park without being mugged. (Hell, you'll hardly smudge your pajamas.) But the protests against economic inequality that are rumbling through our cities right now are also a sign of the dissonance that hums just below the surface of this new urban era. They're a reminder that if the young people occupying Wall Street are going to keep our cities evolving, then the old model -- gentrification by fiat -- will need to change, as well.

This new column will focus on how we forge our new urban future and how we create cities that reflect our values. We will cover this intersection of innovation and inequality, of urban design and the problem of poverty, and how one might help solve the other. Cities today are cleaner, healthier, safer and greener. They're also more expensive. But wealthier, snazzier cities needn't be gilded jewel boxes for the 1 percent. Better transit, smarter development and improved amenities can benefit those who need them most. And there's reason to be optimistic that they will, because the generation that will retrofit our old cities with new ideas is the same one that's currently developing an instinctual aversion to economic unfairness.

In hindsight, we could have seen this new urban groundswell coming. Two or three decades ago, cities were suffering from a toxic stew of debt, crime, poverty and drugs. Corruption at many levels was often the status quo, and "Murder Capital of America" became a dubious buzz phrase that was passed from city to city like a baton. But by the early '90s, for an amalgam of reasons that have been debated ever since, things began to shift. The crack epidemic receded. Cities got safer. "Friends" debuted.

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By the time Rachel quit her job at Central Perk, young people with money and college degrees were inundating cities like a flash-flood. Blight withdrew, and entire neighborhoods were remade overnight. Some longtime residents were forced out by rising rents, while others quickly became millionaires as their property values soared. Among the new arrivals themselves, there was a hasty hashing out of the rules: whether development should trump preservation, whether you should pay a brokers' fee, whether babies could be brought to bars. Some worried that cities like New York were losing their edge. Tiny culture wars erupted (Hasids vs. hipsters! bicyclists vs. drivers!) as everyone tried to figure out the new pecking order, the new urban way of life.

But it didn't take long for the questions to become even bigger, the battles more fierce, and that's when cities really began to transform in ways both profound and permanent. Big changes were brought up for discussion, changes that would have been considered insane just a few years earlier. Do the streets really belong to cars, or to bikes, streetcars and sidewalk cafes? Should we forget about manufacturing and focus on knowledge- and service-based economies? What can we do with the unused spaces -- the empty lots, the abandoned islands -- to create the cities of our dreams?

Those questions led directly to the bicycle boulevards, streetcars and revitalized waterfronts that have turned the urban renaissance into a self-perpetuating machine. The more innovative cities became, the more talented people wanted to live in them. The more talented people arrived, the more innovation they generated. Take Ryan Gravel, a quintessential example of how minor players with off-the-wall ideas are tweaking their own cities according to a new set of ideals. In 1999, Gravel needed a thesis topic for his joint degree in architecture and urban planning. The 27-year-old grad student knew one thing about Atlanta: It was a bitch to get around. So he created a plan for the BeltLine, a 22-mile "emerald necklace" of parks, light rail and new development encircling the city. Today, it's actually being built. The improbable project seems to have come to fruition through sheer enthusiasm: "Neighborhood groups, church groups, pedestrian advocacy organizations, cycling organizations," says Gravel. "There was a huge groundswell of public support, and it came from the bottom up. The people of Atlanta owned this project before the mayor did."

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This is the case with so many of these initiatives. Plans to tear down the Claiborne Expressway in New Orleans started small, too, but now it looks as if it might really happen. Half a century ago, the city erected the elevated highway by punching through the historic neighborhood of Treme, destroying an oak-adorned boulevard and creating a high-crime corridor along the way. After Hurricane Katrina, as the municipal government prepared a new master plan for the city, locals fought to remove the expressway and restore the elegant landscaped boulevard. What started as a quixotic campaign has gained public support -- a recent poll shows 57 percent in favor of the plan. Even Mayor Mitch Landrieu, while not yet officially behind it, called the proposal a "game changer."

The bikeways of Minneapolis also caught on in a way no one could have foreseen. What once sounded like a boondoggle to some is now the envy of cyclists the nation over. The number of people using the system to get to work nearly doubled between 2005 and 2008, and the city now has the second-highest percentage of bicycle commuters in the country. The linchpin of the network, a five-and-a-half mile former railway bed that acts as a two-wheel superhighway tying the network together, has become a model for other systems.

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Why make bicycles a centerpiece in a city so cold that its buildings are linked by enclosed footbridges? Because cities are so concerned about becoming the next Detroit, swept away by cultural and economic tides, that they'll consider just about any new idea, no matter how outlandish, thinks Ryan Gravel. That's part of what made the BeltLine a reality, he says: elected officials panicking at the thought of young people -- talented, entrepreneurial people like himself -- fleeing Atlanta. "They want something totally different," says Gravel of this demographic. "They don't want golf clubs and cul-de-sacs and strip malls. They'd rather be talking to their friends on their iPhones than be driving around." The data bears this out. Surveys show young people are less interested in living in the suburbs than their parents were, and today fewer kids get their driver's licenses when they're eligible than they did 30 years ago.

What sounds like a no-brainer to some, however, is unwanted transformation to others, and the rapid changes sweeping through cities haven't converted everybody. The rise of the Tea Party, for one, has slammed the brakes on more than a few projects. One big one got the ax last year when New Jersey Gov. Chris Christie halted construction on the ARC Tunnel, which would have added a much-needed new rail corridor between his state and Manhattan. California's planned bullet train, with its ballooning price tag, has made it a target for deficit hawks nationwide.

Still others look at rooftop farms and bike trails and sleek new trains and see a theme park. In fact (cue the pipe organ) they see something that looks ominously like Disneyfication. But bemoaning the Disneyfication of your city isn't just a superb way to sound like a cranky old fart. It's a form of nostalgia that argues against that which keeps cities alive: constant change.

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There's a whole book devoted to this grousing called "The Suburbanization of New York," in which longtime residents pine for the days when rent was a dollar and your local mugger knew you by name. One essayist in the book revisits the Tribeca playground of her youth, a "simple wood and red-metal playground, patchy lawn, community garden and dilapidated gazebo," and is saddened to find "$1 million worth of shiny equipment." Another writer misses her Greenwich Village of yesteryear: "The halls smelled like drains. The streets were littered, and the facades were shabby ... I was in heaven."

But this is absurd. Complaining about big-box stores squeezing out the mom-and-pops has merit. And whining about yuppies who spend all day shopping in SoHo can be justified (it's also fun). But romanticizing litter, blight and dead grass is a luxury that's about as elitist as you can get. Innovative -- and yes, shiny -- mass transit is saving our cities from being strangled by congestion. Families, no matter how unhip, add social cohesion to communities. And it's true, cities are getting cleaner, which some people don't like. (There's no shortage of nostalgia for "gritty.") But we can't put smog back in the air, sludge back in the waterways, or needles back in Tompkins Square Park. Maybe as a concession, New York's next cool new innovation can be a drain-scented room freshener.

There is one particular complaint that's valid, however, a key concept that reeks of the magical world of Disney and continues to haunt our cities: the idea that poor people should be somewhere else. Many cities are starting to look like super-tidy cores of white people zipping down kelly-green bike lanes, surrounded by destitute neighborhoods that aren't gritty in the good way.

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The dirty secret of our urban rebound is that today's cities are more economically segregated than they were in the '70s. By 2005, only 4.6 percent of the homes for sale in New York were affordable to people making the city's median income. In L.A., rental prices doubled in a decade while wages grew by less than one-fifth. And Washington, D.C., has become the wealthiest city in America by income -- even though the jobless rate in its poorest neighborhood is the highest in the country.

In his book "The Triumph of the City," Edward Glaeser argues that poverty is a sign of a healthy city because it means that poor people moved there seeing economic opportunity. This may be. But the inescapable truth is that the new urban reality we've created -- the one with spiffed-up boulevards and cutting-edge transit and high-design parks and bike lanes and BeltLines -- is more expensive than the one that existed before. Without the right planning and policy, these cities risk becoming sleek, efficient, hollow places, drained of their anything-can-happen dynamism. Norman Rice, Seattle's first and only black mayor, put it candidly in 2006: "I am concerned and I am frustrated because I don't know what the alternatives [to gentrification] are. It clearly isn't racist; it's economics. The real question you have to ask yourself is: Is this good or bad?"

There's no simple answer to questions like these. But if a city is anything, it's a marketplace of ideas -- and so a likely place to find solutions to seemingly intractable problems. They say that cities tend to decline similarly but succeed in their own unique ways. Those successes are what will make our newly urbanized world the incredible place where everyone wants to live.