A 1930 powerhouse on the upper Yoshii River
The Kamisaibara Power Station Main Building is a reinforced concrete powerhouse of 1930 standing in the Taruhara district of Kamisaibara, Kagamino, Okayama Prefecture, and it was listed as a Registered Tangible Cultural Property on 29 November 2006. Water reaches it down an open channel fed by weirs on the Yoshii River and three of its tributaries, and leaves through a tailrace that supplies the next station downstream.
The plan is plain; the proportions are not. A generator hall of 16 metres by 14 metres fills most of the 288 square metres of floor area, with the office and rest rooms pushed out from it as low side wings. Narrow vertical windows run round all four elevations, set high enough to light the machine floor without putting glass where a crane might swing.
Look up inside and the reason for the shape becomes obvious. The roof rests on a Pratt truss whose rise has been deliberately flattened, so the hall keeps a tall interior under a shallow roof. A generator has to be lifted, turned and lowered back onto its bed during overhaul, and the ceiling height was bought with truss geometry rather than with roof pitch.
Generation started in July 1930. The station is rated at 2,700 kilowatts and remains part of the Chugoku Electric Power hydro fleet.
Why the building was registered
Nine structures of this station went onto the register together on 29 November 2006. Eight of them are civil engineering works or site works: weirs, settling basins, a confluence basin, a head tank, stone retaining walls. Only the Kamisaibara Power Station Main Building is classed as a building. All nine were accepted under the criterion that they contribute to the historic landscape of the country.
The word here is registration, not designation. The register was set up in 1996 for buildings that are still in everyday use, and it asks an owner to notify the authorities before major alteration rather than to freeze the fabric. A Registered Tangible Cultural Property therefore keeps working, which is exactly what has happened here.
What gives the building its weight is the sequence it sits in. Between 1920 and 1932, Chugoku Godo Denki, a predecessor of Chugoku Electric Power, built a chain of run-of-river stations along the upper Yoshii: Iri in 1920, Heisakubara in February 1928, Kamisaibara in July 1930, Okutsu in February 1932. Water discharged at Heisakubara is collected again and sent here; water discharged here is collected again and sent to Okutsu. The powerhouse is one link that has never been taken out of the chain.
What to look at
Start with the wall surface. This is concrete of 1930, cast in an era when Japanese engineers were still working out how a reinforced concrete industrial shell should be detailed, and the elevations carry the shallow pilaster strips and simple string course that period used to keep a blank wall from reading as blank.
Then the ground the building occupies. There is very little flat land in this valley, and the terrace under the powerhouse was cut, not found. Stone retaining walls hold the site up on the west and north sides, and a second pair of straight walls climbs the slope to either side of the penstock that drops from the head tank about 250 metres above. Those walls are registered in their own right.
The tailrace is worth a moment as well. It runs out of the building and into a long concrete channel belonging to the Okutsu station, where the used water is combined with fresh water and sent on. Standing at the Kamisaibara Power Station Main Building, you are looking at roughly the midpoint of a river that gets worked four times before it reaches the Tsuyama basin.
Visiting
This is an operating power station, not a visitor attraction. There is no admission charge, no ticket office and no published opening time. The exterior can be seen from the public road that runs along the valley.
To look at the plant itself, Okayama Prefecture asks visitors to arrange it beforehand with the Tsuyama Power Office of Chugoku Electric Power, on 0868-27-0275. Ask about photography when you call, since the buildings stand inside the operator's fence.
Kamisaibara is the northernmost district of Kagamino, close to the Tottori border. National Route 179 runs through it on its way from Tsuyama to Ningyo Pass. By public transport, the nearest railheads are Tsuyama Station and Inno-sho Station on the JR Kishin Line; Chutetsu Hokubu Bus works the Tsuyama to Okutsu Onsen and Ishigoshi route through the district, and Kagamino town publishes the current timetables. Winters here are heavy, and the road over the pass is a snow route, so a visit between late spring and autumn is easier.
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Q&A
- Can I go inside the Kamisaibara Power Station Main Building?
- Not without arranging it in advance. Okayama Prefecture gives 0868-27-0275, the Tsuyama Power Office of Chugoku Electric Power, as the contact for anyone wishing to view the facilities. The exterior is visible from the public road at any time.
- Is there an admission fee for the Kamisaibara Power Station Main Building?
- No. The site is a working generating station rather than a museum, so no fee and no opening hours are published.
- Is the power station still generating electricity?
- Yes. Chugoku Electric Power lists Kamisaibara Power Station on the Yoshii River system with an output of 2,700 kilowatts, and Okayama Prefecture records all nine registered structures as facilities in current service.
- How old is the Kamisaibara Power Station Main Building?
- It was built in 1930 and generation began in July of that year, which makes it a contemporary of the Heisakubara station upstream, completed in 1928.
- How do I reach Kamisaibara without a car?
- Take the JR Kishin Line to Tsuyama or Inno-sho, then the Chutetsu Hokubu Bus service towards Okutsu Onsen and Ishigoshi. Kagamino town publishes the timetables on its public transport page. Services are infrequent, so check the return departure before you set out.
Basic Information
| Name | Kamisaibara Power Station Main Building |
|---|---|
| Location | Taruhara 1163-2, Kamisaibara, Kagamino-cho, Tomata-gun, Okayama Prefecture |
| Designation | Registered Tangible Cultural Property (structure) |
| Year Designated | Registered 1930 building on 2006-11-29 |
| Quantity | 1 building |
| Dimensions | Reinforced concrete, single storey; building area 288 square metres; generator hall 16 metres by 14 metres; tailrace included |
| Owner | Chugoku Electric Power Co., Inc. |
| Public Access | Operating facility. Exterior visible from the public road; viewing of the plant by prior arrangement with the Tsuyama Power Office, 0868-27-0275 |
References
- National Cultural Properties Database, Agency for Cultural Affairs: Kamisaibara Power Station Main Building
- https://kunishitei.bunka.go.jp/heritage/detail/101/00006058
- Cultural Heritage Online, Agency for Cultural Affairs: Kamisaibara Power Station Main Building
- https://online.bunka.go.jp/heritages/detail/185963
- Okayama Prefecture, Cultural Properties Division: Registered Cultural Properties in Okayama Prefecture
- https://www.pref.okayama.jp/page/detail-50777.html
- Okayama Prefecture: Kamisaibara Power Station Facilities (PDF)
- https://www.pref.okayama.jp/uploaded/attachment/260992.pdf
- Chugoku Electric Power Co., Inc.: List of hydroelectric power stations
- https://www.energia.co.jp/energy/general/water/water_all.html
- Kagamino Town: Route buses and public transport
- https://www.town.kagamino.lg.jp/soshiki/22/2132.html
Last verified: 2026.09.08