Over a total length of 77 kilometers and with a gradient of 26 meters, 29 Lech canals run through the urban area. You can see their importance for the medieval city in the Ulrichs and Lechviertel. With a total length of more than three kilometers, four Lech canals - Schwallech, Hinterer, Mittlerer and Vorderer Lech - flow through the former craftsmen's quarter. The Vordere Lech is the extension of the Lochbach, which flows over the aqueduct of the waterworks at the Red Gate and through the small water tower into the Ulrichsviertel. In the Schwallech, the Lech water flows from the Hochablass into the Lechviertel. At the Schwall, a narrow tongue of land near the monastery of St. Ursula, the Schwallech divides into the Middle and Rear Lech. The two Lech canals flow parallel and close to each other before they merge after the Brechthaus at the alley “Auf dem Rain” to form the Stadtbach. Shortly before that, the Vordere Lech flows into the Mittlerer Lech.