Located on the island of Honshu, at the mouth of the Yodo River on Osaka Bay about 400km west of Tokyo, Osaka is one of Japan's largest cities and the centre of the second largest metropolitan area in Japan. Although the origins of Osaka can be traced back to the 5th century BC, the city started developing significantly after the construction of the Osaka castle in 1586. The daimyo Toyotomi Hideyoshi encouraged merchants from all over Japan to settle in the area, laying the foundations for the development of Osaka as a the commercial capital of Japan. The city of Osaka has a population of 2.6 million inhabitants. Osaka is famous for its nightlife and its culinary delicacies.