South Korea , officially the Republic of Korea (, ) and commonly referred to as Korea, is a sovereign state in East Asia, constituting the southern part of the Korean Peninsula. The name Korea is derived from the ancient Kingdom of Goguryeo, also known as Koryo. Highly urbanized at 92%, Koreans lead a distinctive urban lifestyle with half of them living in the Seoul Capital Area, the world's second largest city with over 25 million residents and a leading global city with the fourth largest economy, rated in 2016 as the world's most livable megacity and safest city to live in. Highly mountainous, Korea is a popular winter sport destination in Asia, hosting the 2018 Winter Olympics.