Busan, formerly romanized as Pusan and now officially is South Korea's second most-populous city after Seoul, with a population of over 3.5 million inhabitants. It is the economic, cultural and educational center of southeastern South Korea, with its port—Korea's busiest and the fifth-busiest in the world —only about 120 mi from the Japanese islands of Kyushu and Honshu. The surrounding "Southeast Economic Zone" (including Ulsan and South Gyeongsang) is South Korea's largest industrial area.