Sennin Buro is a famous rotenburo (open air bath) at Kawayu Onsen in Hongū. Kawa-yu Onsen is a natural wonder, geothermal heated water percolates up through the gravel banks of the river.
This giant open-air bath is created by damming the Ohtou River and letting the natural hot spring waters fill the pit. Because much depends on Mother Nature, the pool tends to be a different size every year. The water springs from the riverbed at a hot 73 degree but then mixes with the crystal clear waters of Ohtou River, bringing the temperature down to about 40 degree. The pool is enclosed along the perimeter by a reed screen, leaving the rest open to the skies and stars for you to enjoy while soaking in the warm waters.
Sennin Buro onsen is only available during winter from December to end of February, with a capacity of nearly 1,000 people (or ”sennin” in Japanese) can be entered when wearing a bathing suit.
Address: Hongucho Kawayu, Tanabe, Wakayama 647-1717, Japan
Opening Hours: December – February: 06:30 – 22:00
Holidays: Open every day during the period
Parking: 50 Free parking spots
Ease of Access
Ryujin Bus from JR Kii-Tanabe Station and get off at “Kawayu Onsen” (approximately 90 minutes)
From the Kii-Tanabe Interchange on the Hanwa Expressway, take National Route 42, 311 towards Hongu for approximately 54 km
Sennin Buro sets in Kawayu Onsen, which is a geological thermal wonder located on the Oto River, a tributary of the Kumano-gawa River. “Kawa” means “river” and “yu” means “hot water”. In Kawayu Onsen hot spring water bubbles to the surface of the crystal clear river.
The defining feature of Kawayu Onsen is the river. On the north side is a collection of places to stay including a diversity of ryokans, minshukus, and hotels. On the south side of the river is a green forested mountainside. The world heritage Kumano Hongu Taisha and Kumano Kodo pilgrimage routes are close by.
One of the best ways to enjoy Kawayu Onsen is to soak in the soft evening light while watching the warm mist from the river rise slowly into the clean mountain air. You can dig your own bath or bathe in a prepared one.
Yukemuri Tourou is the event of Lanterns in the hot-spring steam, which is held from 8:00 pm to 10:00 pm on Saturdays. Lanterns are placed around the bath to create the scenic atmosphere of a hot-spring town in the night.
Kawayu Onsen Map: https://www.hongu.jp/wp-content/uploads/2021/01/DOC210102-20210102092721.pdf