South Korea. Flying over East Asia, astronauts on the International Space Station (ISS) took this night image of the Korean Peninsula. Unlike daylight images, city lights at night illustrate dramatically the relative economic importance of cities, as gauged by relative size. In this north-looking view, it is immediately obvious that greater Seoul is a major city and that the port of Gunsan is minor by comparison. There are 25.6 million people in the Seoul metropolitan area -- more than half of South Korea’s citizens -- while Gunsan’s population is 280,000. [NASA]