In the Edo Period, a certain merchant took action to develop the river.
You may not be able to see the wall itself. You can, however, feel it. The Hozugawa River flows fast along many, many bends. Even so, the ferryman endeavors to keep from manually turning the boat. This is the work of the piled stone walls. Carefully engineered and placed at key points along the river, they naturally follow and control the currents and prevent the boats from forcefully running aground.