Yunomine Onsen Kumano Kodo

Yunomine Onsen is Japan's oldest documented hot spring with 1,800 years of continuous recorded use, and its legendary Tsuboyu — a tiny stone bath set within a volcanic steam vent in the Yuno river itself — is the only hot spring in the world to hold UNESCO World Heritage Site designation as part of the Sacred Sites and Pilgrimage Routes of the Kii Mountain Range. The spring's bicarbonate water changes color seven times daily as mineral composition shifts with temperature and flow variations, a scientifically remarkable natural phenomenon that has been observed and revered by pilgrims walking the Kumano Kodo since the Heian imperial era. Bathing at Yunomine after walking the ancient Nakahechi pilgrimage route to Kumano Hongu Taisha shrine connects visitors to 1,800 years of continuous Japanese spiritual and therapeutic tradition — the deepest roots of Japan's hot spring culture.