Okutama Onsen — Moegi-no-yu 奥多摩温泉 もえぎの湯
The water rises from the oldest layer in Japan, ten minutes from the station.
The water springs from the 古生層, the Palaeozoic layer, which is considered the oldest in Japan, and the facility states that it uses the spring water one hundred per cent, with nothing added.
Tokyo
Oku-Tama