The Cheonggyecheon Restoration Project

http://environment.guardian.co.uk/conservation/story/0,,1936011,00.html

...in a revolutionary act of ecological restoration that is now being examined around the world, the city of Seoul, under the leadership of the then mayor, Lee Myung Bak, pledged in 2002 to restore the river, tear down the motorway and create a five-mile long, 800-yard wide, 1,000-acre lateral park snaking through the city where the river once ran...
The city had beefed up its bus service and given people options to avoid the motorway, and the effect on the environment was remarkable. Hwang says: "We found that surface temperatures in summer along the restored river were an average 3.6 degrees Centigrade lower than places 400 metres away. The river is now a natural air conditioner, cooling the capital during its long hot summers. Average wind speeds in June this year were 50% higher than the same period last year. It was extraordinary. Also, many birds came back, plus fish, insects and plants. The variety of wildlife has vastly increased since we tore up the road."

http://www.metro.seoul.kr/kor2000/chungaehome/en/seoul/main.htm