Seoul is 'The old city'. Seoul is chosen to capital city, because there are river and mountains also it s the center of korea.

 There is Han river in Seoul.  'Han' means big or large.

 Mountains of Hanyang protected enemies to king and queen.

 There were 4 big doors in Hanyang.East door, west door, south door and north door are them.

 There were markets too in Hanyang. Sijeon was licensed markets and nanjeon was unlicensed markets.

 Usually Yangban used Sijeon and poor people used nanjeon.

 During 600, Seoul is capital city in Korea. Seoul is really 'The Old City'