Why are these cities clustered the way they are? Why is

>>78948283
because they all used to be independent countries.

>>78948283
>The Rhine-Ruhr metropolitan region (German: Metropolregion Rhein-Ruhr) is the largest metropolitan region in Germany with over 11 million inhabitants. It is of polycentric nature and the only megacity in Germany. It covers an area of 7,110 square kilometers and lies entirely within the federal state of North Rhine-Westphalia. The Rhine-Ruhr metropolitan region spreads from Dortmund-Bochum-Essen-Duisburg (Ruhr Area) in the north, to the urban areas of the cities of Mönchengladbach, Düsseldorf (the state capital), Wuppertal, Leverkusen, Cologne (the region's largest and Germany's fourth largest city), and Bonn in the south. The location of the Rhine-Ruhr at the heart of the European blue banana makes it well connected to other major European cities and metropolitan areas like the Randstad, the Flemish Diamond and the Frankfurt Rhine Main Region.
The metropolitan area is named after the Rhine and Ruhr rivers, which are the region's defining geographical features and historically its economic backbone.

>>78948424
>Historically, most of the Ruhr area was for the most part characterized by heavy industry since the age of industrialisation in the late 19th and early 20th century. Since the Middle Ages, Cologne, Dortmund and other cities were important regional trading cities, but during the 19th century the city of Düsseldorf grew to become the administrative center of the region and since 1945 its political capital.
>Today, the Rhine-Ruhr metropolitan region accounts for roughly 15% of the GDP of the German economy, which would place it as the 3rd largest GRP of metropolitan area in the European Union and the 16th largest GDP in the world. Despite this size, the Rhine-Ruhr region as a whole often lacks international competitiveness from the lack of a unified presentation, in which cities and urban areas within it, often pursue a separate investment policy against each other.[17]
>From within, Düsseldorf, Essen and Cologne are by far the largest economic centers,[18] with specialisation in financial/high tech and insurance/multi media services respectively. Other major economic centers are Bonn and Dortmund. The region is home to twelve[19] Fortune Global 500 companies, among them E.ON AG, Essen, Deutsche Post AG, Bonn, Metro AG, Düsseldorf, Deutsche Telekom AG, Bonn, ThyssenKrupp AG, Essen/Duisburg, RWE AG, Essen, Bayer AG, Leverkusen, Franz Haniel & Cie. GmbH, Duisburg, Evonik Industries, Essen, Hochtief AG, Essen and the Henkel Group, Düsseldorf.