The term 'Ruhr HUB' is a combination of two words, 'Ruhr' and 'HUB'. The Ruhr is a region in Germany, located in the state of North Rhine-Westphalia. It is known for its industrial heritage and is home to many large cities, including Essen, which is the answer to the crossword puzzle. Essen is the largest city in the Ruhr region and is an important economic center. It is also home to several universities and research institutions, making it an important HUB for innovation and technology.