Seoul, officially the Seoul Special City, is the capital and largest metropolis of South Korea. Seoul has a population of 9.7 million people, and forms the heart of the Seoul Capital Area with the surrounding Incheon metropolis and Gyeonggi province. Ranked as an alpha world city, Seoul was the world's 4th largest metropolitan economy with a GDP of US$635 billion in 2014 after Tokyo, New York City and Los Angeles.