The state of North Rhine-Westphalia (in German "Nordrhein-Westfalen" or short NRW) is highly industriated and, as the name shows, the Rhine is the main river that flows through this region. Ruhr, Wupper, Lippe and Erms are the other rivers that are situated in Europe's largest industrial concentration. Almost 18 million people live in this region, more than 50 per cent of them in one of the big cities like Düsseldorf, Dortmund, Cologne or Duisburg. Altogether NRW has 30 cities with more than 100.000 inhabitants - more than 20 per cent of all Germans live in this federal state.