Earlier quoted context omitted.
Subways are underground
Is this meant to contribute in some way? I honestly have no idea what this seemingly random phrase is supposed to convey.
I'm writing this from the 11th floor apartment in an apartment town suburb 30 minutes by subway from Seoul. It is dead silent. Very little traffic, and everything is walking distance. From above ground you don't hear the subway at all. Sound insulation in this apartment is pretty good so I never hear my neighbors (actually there's only 2 apartment units on each floor).