Colonia Claudia Ara Agrippinensium was the Roman colony in the Rhineland from which the German city of Cologne developed.
It was the capital of the Roman province of Germania Inferior and the headquarters of the military in the region. With the administrative reforms under Diocletian, it became the capital of Germania Secunda. Many artifacts from the ancient city survive including the arch of the former city gate with the inscription 'CCAA', which is today housed in the Romano-Germanic Museum.