Frank Langfitt

In the 1920s and 1930s, Shanghai was one of the world's most exciting — and notorious — cities. But all that came to an end in the middle of the last century, when the Communists took charge.

Over the past decade or so, though, a vibrant Shanghai has re-emerged. Today, it's a dynamic city of 23 million, with a skyline that dwarfs Manhattan's.

One of China's biggest criminal trials opens Thursday, and its lurid details make for a sort-of Communist Party film noir. The wife of an ambitious Chinese politician is accused of murdering a British businessman. Her powerful husband allegedly blocks the police investigation, and the police chief, fearing for his life, takes refuge in a U.S. consulate and implicates the wife in the killing.

China became a majority urban country this year. No nation has shifted so quickly from rural to urban than China, where more than half of the people now live in urban areas.

Everyone is familiar with megacities like Beijing and Shanghai, but they are just a tiny part of China's urbanization story. The country has more than 160 cities with populations of a million or more — places most of the world is only vaguely familiar with, if at all.

Deng Jiyuan and Feng Jianmei, a couple from northwest China's Shaanxi province, have a 6-year-old daughter. Under China's complicated birth calculus, they were barred from having another child. But they tried anyway.

"We planned this pregnancy because our parents are old, they want us to have another child," Deng, 30, explained by cellphone last month from his home in Shaanxi.

That decision led to a sequence of events that has ignited a firestorm and renewed debate over the country's one-child policy.

Back in early April, a Philippine navy frigate tried to arrest Chinese fishermen accused of poaching sharks and giant clams.

But more is at stake than a boatload of seafood.

Neighboring countries say confrontations like this are growing as China asserts claims to territory well beyond its coastline. And analysts think China is testing America's resolve in the region.

Philippine officials say China still has more than 30 boats in the contested area, which is widely known as Scarborough Shoal, though the Chinese call it Huangyan Island.

Mongolia, the land of Genghis Khan and nomadic herders, is in the midst of a remarkable transition. Rich in coal, gold and copper, this country of fewer than 3 million people in Central Asia is riding a mineral boom that is expected to more than double its GDP within a decade. The rapid changes simultaneously excite and unnerve many Mongolians, who hope mining can help pull many out of poverty, but worry it will ravage the environment and further erode the nation's distinctive, nomadic identity.

Last of four parts

Mongolia, the land of Genghis Khan and nomadic herders, is in the midst of a remarkable transition. Rich in coal, gold and copper, this country of fewer than 3 million people in Central Asia is riding a mineral boom that is expected to more than double its GDP within a decade. The rapid changes simultaneously excite and unnerve many Mongolians, who hope mining can help pull many out of poverty, but worry it will ravage the environment and further erode the nation's distinctive, nomadic identity.

Third of four parts