Essen is the second largest city in the Ruhr, which is the largest metropolitan area in Germany. Its population of 583,393 makes it the ninth largest city in Germany, as well as the fourth largest city in the federal state of North Rhine-Westphalia. On the banks of the Ruhr and Emscher, Essen is geographically considered part of the Rhineland and the Greater Rhine-Ruhr region. The Ruhrdeutsch language spoken in the region has strong influences from both Low German (Westphalian) and Low Franconian (Eastern Burgue). The city is home to eight of the 100 largest publicly owned German companies in terms of trading, including three DAX companies, which places it first among all German cities in the number of DAX corporate headquarters. Essen is often considered the energy capital of Germany with E.ON and RWE, Germany's largest energy providers, both located in the city. She is also known for her influence on the arts with the famous Folkwang University of the Arts, its Zollverein School of Management and Design, and the Red Dot Award for Industrial Product Design. In early 2003 the universities of Essen and the nearby city of Duisburg (established in 1972) were merged into the University of Duisburg-Essen with campuses in both cities and a university hospital in Essen. In 1958 Essen was chosen to be the seat of the Roman Catholic Diocese (often referred to as the Ruhrbistum or the Diocese of the Ruhr). The city's notable achievements in recent years include being named European Capital of Culture on behalf of the entire Ruhr region in 2010 and being named Europe's Green Capital for 2017.