An original schematic for this book. Not to scale; not a street-navigation map.
North of the river
Gyeongbokgung, Bukchon and Insadong make a natural walking cluster. Add Cheonggyecheon and Gwangjang Market on another day. Myeongdong sits below the old centre, with Namsan rising to the south.
Across the city
Hongdae and Yeouido suit a west-Seoul day. Gangnam and COEX are south of the river; Itaewon is on the north side. Check the exact station exit before you set off: two exits can lead to quite different walks.