Among these independent provinces were upper Germania. Apparently it had become a province in the last years of the republic. Tacitus also mentions it as the province of Germania Superior in his "Annales" (3.41, 4.73, 13.53). Cassius Dio viewed the Germanic tribes as Celts, an impression given perhaps by Belgica, the name assigned to lower Germania at the time. Dio does not mention the border, but he views upper Germany as extending to the source of the Rhine. It is not clear if he was aware of the Upper Rhine in Switzerland, upstream from Lake Constance. Today the section of the Rhine running through upper Germania is called the middle Rhine.