Several of the oldest cities of northwestern Europe are highlighted in this astronaut photo of 10 August 2011. While the landscape is dotted with clusters of lights from individual urban areas, the metropolitan areas of London (lower left), Paris (center), Brussels, and Amsterdam (upper left) stand out due to their large light "footprints." The metropolitan area of Milan is also visible at image upper right. While each of these cities is, or has been, the capital of a kingdom, republic, or empire – Paris and London have been all three – Brussels is also the capital city of the European Union. To give a sense of scale, the centers of the London and Paris metropolitan areas are approximately 340 km (210 mi) from each other. The image is also oblique making the distance between Paris and Milan (640 km, or 400 mi) appear less than that of Paris to London. In contrast to the land surface defined by the city lights, the English Channel presents a uniform dark appearance. Similarly, the Alps near Milan are also largely devoid of lights. While much of the atmosphere was clear at the time the image was taken, the lights of Brussels are dimmed by thin cloud cover. Image courtesy of NASA.