An oil slick on the surface of the Po River in Italy. The oil comes from a spill earlier this week at a former oil refinery in the Lombardy region of Italy. It is thought to be the work of saboteurs. The oil originally seeped into the Lambro River, a Po tributary. Officials hope that barriers erected in the Lambro will prevent most of the oil from polluting the Po, which provides water to some of Italy's richest agricultural land.