Unfortunately, North Korea and South Korea are not friendly with eachother. Even though they haven't fought in almost 70 years, they are still technicially at war. Subway stations in Seoul are designed to be used as shelters in case people need to hide from fighting. The Seoul subway is wonderfully easy and convenient, but you can also see signs at every station that say "shelter," which reminds you of North Korea's and South Korea's unfortunate relationship.
