Yunomine Onsen (Japan's Oldest Hot Spring)

Yunomine Onsen, a small village along the Kumano Kodo pilgrimage route in Tanabe, Wakayama, is said to be Japan's oldest hot spring, with a documented history of over 1,800 years of continuous use. Since the Heian period, pilgrims traveling to the Kumano Sanzan shrines stopped here to bathe and ritually purify themselves before continuing to the sacred sites, a practice that gave the village lasting religious significance beyond its therapeutic reputation. Its centerpiece, the Tsuboyu bath, is a tiny wooden bathhouse built directly over the natural spring source in the village's central streambed; in 2004 it became the only hot spring bath in the world to be individually registered as a UNESCO World Heritage site, as part of the broader Kii Mountain pilgrimage inscription. The spring water, which changes color several times a day due to its mineral content, is also used in streamside communal cooking pools called yuzutsu, where visitors boil eggs and vegetables in the naturally hot water. The village retains a layout and scale of ryokan inns largely unchanged since the Edo period, with narrow lanes following the stream and steam rising from public foot baths along the way. The Tsuboyu bathhouse itself is periodically rebuilt in its original small wooden form to preserve the historic bathing experience rather than modernizing the structure.