In Kagoshima (and maybe other places as well) they have Sunamushi Onsens. As you know, regular onsens are “hot springs”. Where you get naked and jump into a naturally hot bath with a bunch of old men. Or, if you’re lucky, you can get a private room and jump in with only your girlfriend. 貸し切り！
Sunamushi Onsen is similar, except, there is no water, you don’t get naked, it’s not especially fun if you get in with your girlfriend, and it’s not exactly “hot”, more like, toasty. Read the warning signs!
You change into a simple yukata and no underwear before getting out to the sand pit. Once you’re ready, the old ladies working at the location will dig you a shallow grave. Then you climb in, and they proceed to shovel sand all over your body, except your face.
At first the feeling of being buried by a buncha people with shovels freaked me out. But, I think that only happens to me. Once you are buried, you realize first, that sand is heavy. And two, that this sand is hot!
Kagoshima is famous for Sakurajima, a volcano… Basically right in the middle of the city. This volcano is still active, and just 10-15 years ago, the city was covered in ash most of the time because of it’s frequent spurts. Because of this, the area has many natural onsen, and also, this really hot sand.
It felt great!