Inside the world's biggest drain

On the banks of the Yellow River, China's government is trying to solve an age-old problem. Every year the north of the country faces a drought, while the south gets flooded.

So they are building the world's largest drain. The middle section alone will be 1200 km long and is a bigger engineering project than the Three Gorges dam.

In five years' time, billions of gallons of water will pour from the south, heading to the parched north.

No one knows if it will actually work - but there is no doubt it will help the Chinese economy.

Work started before the financial crisis, but the government's record-breaking stimulus package helped hurry things along.

The BBC's Quentin Sommerville took a look inside.