Percentage of the Muslim population in Germany.
Reddit user: realKkona
North Rhine-Westphalia is the most densely populated area of Germany as well as its industrial heartland. Hence, a lot of immigrant workers end up there. In 2003, when Chelsea’s match against Besiktas couldn’t be played in Istanbul because of security reasons, it was shifted to Gelsenkirchen and it was almost like a home game for Besiktas considering the number of Turks in the area.
And, as Muslims being mainly immigrants, it also reflects the economic prosperity of different regions of Germany. Berlin, being the capital city, is an outlier in the east.