The Lech does not slip quietly past Landsberg — it crashes over a stepped weir at the foot of the old town in a wide curtain of white water, audible from the Hauptplatz on quiet days. The Karolinenwehr was built in 1907 to power a hydroelectric plant; an earlier weir in the same spot dates back to the late Middle Ages, when it powered the mills that made Landsberg's fortune as a salt and grain market.
A footbridge crosses the river just below the weir, with the best photograph angle of the old town climbing the hillside behind. Continue along the right bank for a half-mile riverside walk to the Mutterturm.