In the south the Ahrgau bordered on the Mayenfeldgau on the line from Rheineck up the Vinxtbach stream to the Hohe Acht; in the west it bordered on the Eifelgau and Zülpichgau along the Adenaubach stream as far as the Ahr, along the Vischbach, the Sürsch and the Swist; in the north it bordered on the Bonngau; in the east the Rhine separated the Ahrgau from the Auelgau.