Köln is a German city located on the Rhine River. It is the fourth largest city in Germany and is the largest city in the state of North Rhine-Westphalia. Köln is known for its historical sites, such as the Cologne Cathedral, which is a UNESCO World Heritage Site. The city also has a vibrant cultural scene, with many museums, galleries, and theaters. Köln is an important economic center in Germany, and is home to many large companies.