The Ruhr is a major industrial region of Germany located in the state of North Rhine-Westphalia. It is one of the most densely populated and industrialized areas in Europe, with a population of over 5 million people. The Ruhr is home to many of Germany's largest cities, including Dortmund, Essen, Duisburg, Bochum, and Oberhausen. It is also home to numerous steel and coal production facilities, making it an important economic hub for the country.