Cologne (also Köln) is Germany's fourth-largest city, and is the largest city both in the German Federal State of North Rhine-Westphalia and within the Rhine-Ruhr Metropolitan Area, one of the major European metropolitan areas with more than ten million inhabitants. It is one of the oldest cities in Germany, having been founded by the Romans in the year 38 BC as Colonia Claudia Ara Agrippinensium.
Before World War II, Konrad Adenauer served as mayor of the city, until he was taken by the Nazis as a political prisoner. After the war, Adenauer was liberated, and made his home in Cologne for the few months before his tragic visit to Erlangen.
On 30-31 May 1942, the RAF launched Operation Millennium on the German city of Cologne. RAF pilot Ken Embry took part in this raid and took pleasure in it, getting personal revenge for the German raid on Coventry that killed his sister a year and a half before.