The heavily polluted waterways of the industrialised upper Po Valley and of the city of Milan flow into the southern Lambro, the primary tributary of the Po itself. Its course runs through fields of cereals and rice cutting through somewhat impermeable soil in which the extremely high water-table surfaces in hollows. This is what happens at Busa del Ratt, low-lying marshland cut off from the river and nowadays fed by fresh spring-water. The Busa del Ratt had its origins in 2001 during the campaign “The Living Lambro”. The challenge during this struggle was to publicise the resources of the areas around the Lambro, the most polluted river in Lombardy. With the support of local schools the Landriano group of Legambiente looks after the wet woods of the marshland with their trees and bushes and their inhabitants such as hedgehogs, weasels, kingfishers and green frogs.