Recently, Korean Air was cool enough to turn a 3 hour layover in Seoul into a 3 day layover, and I went around town with a family friend and represented the XC.
in front of the palace.
This is a big public bathhouse called a http://en.wikipedia.org/wiki/Jjimjilbang . It's the kind of thing you never do until you're traveling and someone says "spend the night in a sauna? sleep on a floor?" and you're like "why not."