The term German Coal Valley is a reference to the Ruhr region in Germany, which is an area known for its coal mining industry. The Ruhr is a 4-letter word that is used to describe this region. The Ruhr is located in the state of North Rhine-Westphalia and is home to many cities, including Dortmund, Essen, and Duisburg. The Ruhr has been an important industrial center since the 19th century, and it is still an important economic hub today. The region is also known for its cultural attractions, such as museums, theaters, and parks.