Jjimjilbang
It costs about ￦5000 to to go to a jjimjilbang and about ￦8000 to sleep there overnight (US$5 to $8).  People come to a jjimjilbang and take off their shoes to walk on the heated floor.  They put all their clothes in lockers.  Then they take showers with soap before going into any of the pools or saunas.