Astronaut Alex Gerst captured from ISS the smog of Po Valley, the northern Italy.

Credit: Alex Gerst, ESA, NASA

This view shows the Po River valley under a thick layer of industrial air pollution. The polluted air is effectively trapped by the high walls of the Alps and Appenine Hills, which rise, amphitheater-like, around the valley. As the plume exits the valley it flows eastward into the Adriatic Sea, which from space often appears almost as polluted as the Po Valley itself.

Credit: Wikipedia

Reference: Alex Gerst’s Tweet
See earthview photo gallery: LiVEARTH