It's what is hidden from immediate view that makes cities such great places. Disguised and buried we are forced to seek out complex places that can only be discovered with open eyes. Seoul is a city with a double identity. The street life of Seoul and the underground reality coincide at limited junctions.
Buried pedestrian ways mirror streets above. An Underground shopping network extending more than a quarter mile in Seoul's south side links to subway routes tied to just about every corner of the city. It is part of a cryptic network of public spaces that define Seoul.
There are usually two sides to most things.
Read the entire article on Seoul Underground at Flavorpill