Köln is a city on the Rhine in Germany. It is the fourth largest city in Germany and is the largest city in the state of North Rhine-Westphalia. To locals, it is known as Köln, which is the German spelling of the city's name. It is a major cultural center and has a long history, having been founded by the Romans in the first century AD. It is also home to many famous landmarks, such as the Cologne Cathedral and the Great St. Martin Church.