SHENYANG - The Liaoning provincial capital is known as one of China's old industrial bases. Serious pollution made Shenyang one of the world's 10 most polluted cities about a decade ago.

For most local residents in the northeast city, the collective impression of their home is that "Stains always stick to gauze masks and white collars easily turn dirty in just half a day."

In Tiexi, a district southwest of the downtown area, about 20 years ago it was home to 90 large- and medium-sized state-owned enterprises, about 90 percent of the city's total.

Chimneys belching out choking gas and pungent rivers had driven away many residents, including Li Shuyong when he was young.

Now 50, Li moved back here last year into a new apartment with his family. The district's efforts to turn cleaner and greener prompted the move.

Most of the polluting factories have now been moved out of the downtown; the area is now filled with an auto trading zone and features grasslands, roadside parks and winding purified rivers.

"It is so beautiful, I could hardly believe my eyes," Li said.

Shenyang, one of the 2008 Olympic co-host cities, launched a pollution-control campaign in 2001 with an investment of around 70 billion yuan (US$10.22 billion).

More than 4,000 chimneys and 7.27 million square meters of illegal constructions were dismantled in five years, creating space for parks and forestation projects.

In 2004, Shenyang was named China's model city for environment protection. The following year, it was honored with the title "city of forest" after raising its forestation rate to 40 percent from nearly 24 percent five years earlier.

Last year, the city registered a record 323 days of good air quality, a sharp increase from 162 days in 2001. The blue skies were due to its efforts in promoting clean energies, treating gas emission and improving its heating infrastructure system.

More than 30,000 birds of various species now nestle on Bird Island, a populous tourist attraction in the city's east.

"There is not a single cage or net on the island. The birds have everything they need here so we don't need to force them to stay," said Wang Daoxian, nicknamed "China's bird king."

He is now taking care of the Shenyang bird kingdom, the third he has initiated in China under the cage-free principle.

The other two are in Guangzhou, capital of Guangdong Province, and Kunming, capital of Yunnan Province, both famous for their favorable climate and environment.

Environment protection has not only improved Shenyang's ecological system, but also enhanced its economic capacity. It is now listed among the country's top-10 economically vigorous city list.

"We have been exploring a path to sustain industrial growth while improving the environment," said Chen Zhenggao, the city's Party chief two years ago. He was promoted to provincial governor earlier this year in recognition for his achievements in rebuilding Shenyang.

Between August 6 to 12, the city will host 12 Olympic football matches.