Seoul, officially the Seoul Special City, is the capital and largest metropolis of South Korea. Seoul forms the heart of the Seoul Capital Area. 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. International visitors generally reach Seoul via AREX from the Incheon International Airport, notable for having been rated the best airport for nine consecutive years (2005–2013) by the Airports Council International. In 2015, it was rated Asia's most livable city with the second highest quality of life globally by Arcadis, with the GDP per capita (PPP) in Seoul being around $40,000. In 2017, the cost of living in Seoul was ranked 6th globally. In 2018, Seoul's real estate market was ranked 5th in the world for the price of apartments in the downtown center.