Osaka is the third largest city in japan, with a population of over 2.6 million (2016). It forms a center of Japanese industry and commerce. Situated at the mouth of the Yodo River, the city was famous for a number of canals connected with rivers and the sea that formed a great network of watercourses until the middle of the 19thcentury. Consequently, the city was once called the “Water Metropolis”. Most of the watercourses have been reclaimed and reconstructed into streets and highways, but they once played an important role in the development of Osaka as a commercial capital.