A global explosion of urban growth and the rise of the megacity could help resolve some of the world's deepest problems, from overpopulation to environmental devastation.
In an upbeat assessment, senior international business and political figures told a forum in New York that along with the obvious challenges, they saw huge opportunities in the rush to urbanization.
In 1800, just 3% of the world lived in urban areas. Today that figure has passed 50% and by 2050 it will likely reach 70%, with cities like New York, Mexico City, Moscow and Shanghai growing exponentially.
Mexican telecoms tycoon Carlos Slim, named by Forbes as the world's richest person, said that bringing people into urban areas is the only way for countries to cope with already inevitable population growth.
"If there were not big cities the service will not be affordable for the population," Slim told the panel at the annual meeting of the Clinton Global Initiative group.
China's foreign minister Yang Jiechi said his country is embracing the urban model with about 120 cities of more than a million people already on the map.
"Cities are very important for generating more GDP and to uplift the whole society," he said. "One percentage increase in urban population will mean a lot jobs, a lot of consumption and a lot of investment."
Of course, packing so many people into tight spaces brings equally big challenges.
It "will create a lot of problems as well, for instance: population pressure, environmental degradation and lack of social amenities," Yang said.
California's lieutenant governor, Gavin Newsom, described the "remarkable challenge to deal with ethnic, racial, religious diversity," and said what matters is "the human capital equation, not just the infrastructure."
Janette Sadik-Khan, the sometimes controversial transport commissioner for New York City, agreed, saying the Big Apple was attempting to make the city more pleasant as it prepares to accommodate an expected extra million people over the next 20 years, on top of the current 8.4 million population.
Sadik-Khan, an avid promoter of bike lanes and pedestrian zones in Manhattan, said that making cities more livable not only attracts a talented, international workforce, but protects the environment.
She pointed to her ban on cars in the Times Square area, saying the measure had boosted retail commerce while improving quality of life for residents. She also noted New York's relatively clean air.
"If you want to save the planet, you should move to New York," she said.
Experts on the panel flagged the boom in communications technology and renewable energy sources as the type of progress that can help cities deal with their expansion as well as heal the world's wider problems.
Newsom spoke of "laboratories of innovation," while China's foreign minister -- highlighting Chinese investment in public transport, eco-friendly cars and solar power -- said: "I believe every challenge, every crisis, will lead to a bumper harvest of innovation."