Wellness

Sennin-buro (Sennin Bath), Kawayu Onsen (Hongū)

Sennin-buro is a winter-only, riverbed open-air bath at Kawayu Onsen in Hongū—formed by damming the Ohtō River and fed by natural hot springs.

Journal

January 31, 2022·3 min read·By Japan Royal Service

In this guide

01Sennin-buro, Kawayu Onsen (Kawayu Onsen, Hongū)

Sennin-buro, Kawayu Onsen (Kawayu Onsen, Hongū)

Sennin-buro is a famous rotenburo (open-air bath) at Kawayu Onsen in Hongū. Kawayu 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 Ohtō River and letting natural hot spring water 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°C, then mixes with the crystal-clear waters of the Ohtō River, bringing the temperature down to about 40°C. A reed screen encloses the perimeter of the pool, while the rest remains open to the sky and stars as you soak.

Sennin-buro is only available in winter, from December through the end of February. It can accommodate nearly 1,000 people (or sennin in Japanese), and visitors may enter when wearing a bathing suit.

General Information

Address: Hongucho Kawayu, Tanabe, Wakayama , Japan
Telephone:
Opening hours (Dec–Feb): 06:30–22:00
Holidays: Open every day during the period
Parking: 50 free parking spots
Admission: Free

Ease of Access

By bus: Ryujin Bus from JR Kii-Tanabe Station; get off at “Kawayu Onsen” (approximately 90 minutes)
By car: From the Kii-Tanabe Interchange on the Hanwa Expressway, take National Route 42 and Route 311 toward Hongū for approximately 54 km

Location

Sennin-buro is in Kawayu Onsen, a geological thermal wonder 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 accommodations, including a variety of ryokan, minshuku, and hotels. On the south side is a green, forested mountainside. The World Heritage Kumano Hongū Taisha and the 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 warm mist rise from the river into the clean mountain air. You can dig your own bath or bathe in a prepared one.

Yukemuri Tōrō

Yukemuri Tōrō is an event featuring lanterns in the hot-spring steam, held from 8:00 pm to 10:00 pm on Saturdays. Lanterns are placed around the bath to create a scenic nighttime hot-spring-town atmosphere.

Website: https://www.hongu.jp/onsen/kawayu/senninburo/
Instagram: https://www.instagram.com/explore/tags/%E4%BB%99%E4%BA%BA%E9%A2%A8%E5%91%82/
Kawayu Onsen Map (PDF):