A short discussion on the orientation of the town planning of the Oppidum of Ubii also known as Ara Ubiorum

Here we discuss the town planning of the Oppidum Ubiorum, also known as Ara Ubiorum, today the city of Cologne in Germany. It has been told that the main east-west axis of the Oppidum was aligned along the sunrise azimuth on Augustus' birthday. We will analyse the orientation of this axis in the framework of the Julian calendar. A possible year of foundation/inauguration is proposed consequently. The orientation according to the natural features of the site of this Roman town along the Rhine is also given and stressed. The features of the site were fundamental in determining the plan of Ara Ubiorum