Passage: The aqueduct began at a spring in the area of Nettersheim in the Urft river valley. It then travelled along the valley to Kall, where it had to overcome the divide between the Maas and the Rhine. The Roman engineers chose this spot because they were able to overcome the divide without resorting to a tunnel or a pump. The aqueduct then ran parallel to the northern Eifel Mountains, crossing the Erft near Kreuzweingarten (in the Euskirchen district) and the Swistbach with an arched bridge. In Kottenforst, northwest of Bonn, it passed through the Vorgebirge highlands. Finally, it ran through Brühl and Hürth before arriving in Cologne. Other springs in the region that met Roman quality and quantity guidelines were also equipped with aqueducts to feed the main line.

Question: What river valley does the aqueduct begin?
Urft