Houtan Park in Shanghai cleans river water

A manmade stream that draws from Shanghai s Huangpu River takes in water so polluted it shouldn t be touched. The stream slows the water, aerates it, and filters it through vegetation, until it emerges clean enough that people can swim in it. The project, called Houtan Park, runs a mile along the riverbank through what was once an urban brownfield, a former industrial site and scar on the urban landscape that is similar to many others in cities around the world. The park, toured by Harvard President Drew