Why it's the capital
Yi Seong-gye, who founded the Joseon dynasty, chose Seoul as his planned capital, and building began in October 1394. Much earlier, Wiryeseong, the capital of the Baekje kingdom, stood within the area of modern Seoul.
Capital of South KoreaSeoul is in the northwest of South Korea. The Han River cuts the city into northern and southern halves, and it is bordered by eight mountains.
Yi Seong-gye, who founded the Joseon dynasty, chose Seoul as his planned capital, and building began in October 1394. Much earlier, Wiryeseong, the capital of the Baekje kingdom, stood within the area of modern Seoul.
Look at the northwest corner of South Korea, just south of the border with North Korea; Pyongyang is to the north-northwest.
Sources: Wikipedia: Seoul