Shima Onsen

Where it sits. Shima Onsen lies at the head of the Shima river valley in the town of Nakanojō, in north-western Gunma Prefecture, about 700 metres above sea level and hemmed in on both sides by forested ridges. The settlement is strung along roughly four kilometres of riverbank and divides into five distinct hot-spring quarters — Yamaguchi, Shinyu, Yubara, Hinatami and Ochiai — each with its own cluster of inns and its own bathing sources. There are more than forty separate springs in the valley. The name means "forty thousand", from a tradition that the water treats forty thousand ailments, and the drinking of the water rather than merely soaking in it is still part of the local practice, with roadside fountains provided for the purpose. Shima was among the first hot springs in Japan designated a National Health Resort Onsen in 1954, a category created for places whose water and setting were judged genuinely therapeutic rather than merely recreational.

The inn everyone comes for. Sekizenkan, in the Yamaguchi quarter, claims the oldest surviving wooden inn building in the country: its Honkan was raised in 1691 and is now a designated cultural property. You reach it across a small arched bridge painted vermilion, which sits directly on the axis of the facade and is the single most photographed object in the valley. Behind the Honkan the property climbs the hillside in stages — the 1930s Sansō wing, and higher still the Toyokuni-kan — linked by a tunnel driven into the slope and a flight of stairs painted the same red as the bridge. The bathhouse called Genroku-no-Yu, built in 1930, is a long tiled hall with five stone tubs, arched windows and a row of small changing cabins along one wall, and it is the interior most often held up as an ancestor of the bathhouse in Spirited Away.

On screen, honestly. The Sekizenkan claim is popular, persistent and unconfirmed. Studio Ghibli has never named the inn as a model, and Hayao Miyazaki's own repeated references for the film point to the Edo-Tokyo Open Air Architectural Museum in Koganei and to a general Meiji-Taishō architectural vocabulary rather than to any single building. The inn itself is careful about this and says only that it is said to be one of the inspirations. What is objectively true is that the ingredients line up almost uncannily: a red bridge crossed to reach a bathhouse, a tunnel through a hillside, a stairway that climbs to lodgings above the baths. Whether Miyazaki drew on Shima directly, absorbed the same source material, or arrived at the shapes independently is not something the record settles. Visitors who come expecting the film and find a working 330-year-old inn instead are rarely disappointed by the exchange.

What the valley itself offers. Upstream, the Shima River has been dammed to form Okushima Lake, whose water turns an intense mineral turquoise that locals market as "Shima Blue"; the shade is at its most saturated in late spring when snowmelt is running and the surrounding beech is bright. A footpath and a road loop the reservoir, and a smaller pool called Oku-Shima Ko sits above it. Down in the village the walking is easy and deliberately old-fashioned: a public bathhouse or two, a wooden Yakushi hall beside Sekizenkan, a scattering of shops selling onsen manjū, and a river path linking the quarters. Several inns operate day-use bathing for a few hours around midday, which is the practical way to sample the water without an overnight stay.

Where it sits in the region. Shima is one of a cluster of Gunma spa towns that includes Kusatsu with its enormous sulphurous flow and Ikaho with its stone staircase, and it is markedly quieter than either. Nakanojō, the parent town, hosts the Nakanojō Biennale, an art festival held in odd-numbered years across disused schools and buildings in the surrounding valleys, which reliably brings a different crowd than the bathing season does. Snow closes little but slows everything; the valley road can require winter tyres from December to March.

Getting there and timing. The approach is by JR Agatsuma Line to Nakanojō Station, then a Kan-etsu bus of about 40 minutes to the Shima Onsen terminus, or by direct highway bus from Tokyo in roughly three and a half hours. Drivers use the Kan-etsu Expressway to Shibukawa-Ikaho and then Route 353. Late April to early June gives fresh foliage and full rivers; the last week of October into mid-November gives the colour. Midweek is materially calmer, and because most inns serve dinner at a fixed hour, the baths are close to empty between six and seven in the evening.