Seoul, officially the Seoul Special City, is the capital and largest metropolis of South Korea. A megacity with a population of more than 10 million, it is the largest city proper in the OECD developed world. The Seoul National Capital Area, which includes the surrounding Incheon metropolis and Gyeonggi province, is the world's second largest metropolitan area with more than 25 million inhabitants. Nearly one of every four South Koreans lives in Seoul; half of South Koreans live in the metropolitan area, as well as 275,000 international residents. Situated on the Han River, Seoul has been a city of national importance for more than 2,000 years. It was founded in 18 BCE when Baekje, one of the Three Kingdoms of Korea, established its capital in what is now southeast Seoul. It continued as the capital of Korea under the Joseon Dynasty and the Korean Empire.
Contributions by Johnhunkim, Sewing, and Kokiri.