Bochum (/ˈboʊxʊm/ BOHKH-uum, also US: /-əm/ -⁠əm, German: [ˈboːxʊm]; Westphalian: Baukem) is a city in North Rhine-Westphalia. With a population of 364,920 (2016), is the sixth largest city (after Cologne, Düsseldorf, Dortmund, Essen and Duisburg) of the most populous German federal state of North Rhine-Westphalia and the 16th largest city of Germany. On the Ruhr Heights (Ruhrhöhen) hill chain, between the rivers Ruhr to the south and Emscher to the north (tributaries of the Rhine), it is the second largest city of Westphalia after Dortmund, and the fourth largest city of the Ruhr after Dortmund, Essen and Duisburg. It lies at the centre of the Ruhr, Germany's largest urban area, in the Rhine-Ruhr Metropolitan Region, and belongs to the region of Arnsberg. Bochum is the sixth largest an