Busan, formerly known as Pusan and now officially is South Koreas second most-populous city after Seoul. It is the economic, cultural, and educational center of southeastern Korea, with its port—Koreas busiest and the 10th-busiest in the world}}—only about from the Japanese islands of Honshu and Kyushu. Its surrounding "Southeast Economic Zone" is now South Koreas largest industrial area. Busan is divided into 15 major administrative districts and a single county, together housing a population of approximately 3.6 million. The full metropolitan area, including the adjacent cities of Gimhae and Yangsan, has a population of approximately 4.6 million. The most densely built-up areas of the city are situated in a number of narrow valleys between the Nakdong and the Suyeong Rivers, with mountains separating most of the districts. The Nakdong is Koreas longest river and Busans Haeundae Beach is also the countrys largest. Busan is a center for international conventions, hosting APEC in 2005. It is also a center for sports tournaments in Korea, having hosted the 2002 Asian Games and FIFA World Cup. It is home to the worlds largest department store, the Shinsegae Centum City.