Duisburg (IPA: [ˈdyːsbʊʁk]) is a German city in the western part of the Ruhr Area (Ruhrgebiet) in North Rhine-Westphalia. It is an independent metropolitan borough within Regierungsbezirk Düsseldorf. With the biggest inland harbour in Europe and its proximity to Düsseldorf International Airport, Duisburg has become an important venue for commerce and steel production. Since the 1970s the Universität Duisburg-Essen (University of Duisburg-Essen) has educated students from all over the world. With 14 departments and more than 33,000 students (as of Winter Semester 2005/06), the University of Duisburg-Essen ranks among the 10 largest German universities. Today's city is a result of numerous incorporations of surrounding towns and smaller cities. It is the twelfth-largest city in Germany and the fifth-largest city in North Rhine-Westphalia with 506,496 residents as of 31 December 2003. The city is renowned for its steel industry. There is still one coal mine in operation, but Duisburg has never been a coal-mining center to the same extent as other places in the Ruhr. All blast furnaces in the Ruhr are now located in Duisburg. 49% of all hot metal and 34.4% of all crude steel in Germany is produced here (status 2000).