2007 is the year that the world's population becomes more urban than rural for the first time. This exciting series explores some of these global cities, and looks at how the challenges of urbanisation, globalisation, citizenship and sustainability are being met and answered.

The most densely populated city in North America is the home of the United Nations and a hub of international finance, art, and entertainment. New York is also a powerful symbol of American culture. The city welcomes immigrants, with more than a third of its population foreign born. And it has successfully dealt with crime--it is the safest large city in the U.S. Though devastated by the terrorist attacks on September 11, 2001, its residents continue their strong recovery.