(Clicking on the photo will show the next photo)
Our room had two private hot springs (in addition to two common ones
that we never used). The first one is indoors and I think is primarily
for washing off before going out into the "rotenburo" or outdoor hot tub.
Of course, all of the water is natural hot spring water (the Japanese
wouldn't have it any other way ... one of the reasons for visiting an
onsen is for the healing aspects of the natural hot spring water).
Private Hotsprings