In 1985, primary school students sent a letter to the mayor of Chengdu, the capital of Sichuan province, begging him to clean up the Fu and Nan Rivers that encircle the city.

CNN: 'The smelly sewer of Chengdu'

The Fu and the Nan were dredged, dikes were built, 24 bridges were built or renovated and 12 new wharves were added.

CNN: 'The smelly sewer of Chengdu'