Japanese Hot and Sour Bath
"... a few of the baths border on the bizarre. For example, a bath house in Osaka offers a curry bath which it asserts is the antidote for almost every nervous disorder and internal illness known to humans. This "treatment" is not just bath water with curry powder sprinkled in; this is a cauldron of hot, soupy, sloppy, muddy curry that you slosh around in until you are cured, said to make the blood circulate faster."
Whatever the reasoning, there are few sights that make me happier than watching a spa attendant ladle dollops of curry onto a kid's shoulder.