Columbia subject headings:
Harvard subject headings:
City walls--Korea (South)--Seoul--History.
Fortification--Korea (South)--Seoul--Description and travel.
Historic sites--Korea (South)--Seoul--Description and travel.
Princeton subject headings:
City walls--Korea (South)--Seoul.
Fortification--Korea (South)--Seoul.
Historic sites--Korea (South)--Seoul.
Seoul (Korea)--Description and travel.