Granite Walls That Made Room for a Power Plant
The Heisakubara Power Station Penstock and Main Building Retaining Walls (平作原発電所鉄管路擁壁及び本館擁壁) are granite retaining walls built in 1928 around the main building of the power station in Kamisaibara, Kagamino Town, Okayama Prefecture, and registered as a Registered Tangible Cultural Property on 29 November 2006.
There are two walls with a combined length of 68 metres. One, 17 metres long, runs beside the penstock that links the head tank with the main building; the other, 51 metres long, wraps around the west and north sides of the building with a bend at the corner. Both are laid in the diagonal Tanizumi pattern.
Neither the penstock nor the generator hall could stand without level ground. In Heisakubara, where the mountains crowd the river, these walls created that ground and hold it in place.
Stone Shaped by the Slope
The Heisakubara Power Station Penstock and Main Building Retaining Walls were registered as structures that contribute to the historic scenery of the country. The Agency for Cultural Affairs describes them as essential for building in a mountain area with little flat land, and notes that their height changes to follow the terrain.
In tanizumi, stones are tilted and dropped in alternately so they lock together and share the load. The walls are not a uniform height because each section was built up to the level of the ground behind it; the rise and fall of the slope shows directly in the line of the top course.
Stone also lines the river faces of the settling basins and reinforces the slope under the spillway. Concrete structures backed by granite walls are a pairing that runs right through this power station.
Standing right beside the main building, these walls also share its setting in a way the more remote stonework does not.
What to Look For
Start with the 51-metre wall that turns from the west side to the north side of the building. Watch how the courses resolve at the corner and where the top line steps up or down, and the shape of the ground behind begins to come through.
Then find the 17-metre wall beside the penstock, built along the pipe's route down the slope. Seeing pipe and stonework together shows that the water route and the earthworks were designed as one.
The diagonal joints in the granite change with the light. Low sun early or late in the day brings out the herringbone-like pattern most clearly.
Visiting the Retaining Walls
The Heisakubara Power Station Penstock and Main Building Retaining Walls are part of the working plant and are managed by Chugoku Electric Power. The company says the station's exteriors can be viewed at any time, but the grounds and any gated or fenced area are closed, so the walls are seen from places where access is permitted.
The address is Heisakubara 1878, Kamisaibara. Chugoku Electric gives about 70 minutes by car via the Innoshō Interchange on the Chūgoku Expressway and about 75 minutes by car via JR Innoshō Station. Deep snow covers the area in winter.
There is no fee. The company's page gives no restriction on photographing exteriors, but operational areas cannot be entered for pictures.
- 📍 Plan Your Visit to Okayama
- Find tours, activities & transport passes near Heisakubara Power Station Penstock and Main Building Retaining Walls
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Q&A
- What are the Heisakubara Power Station Penstock and Main Building Retaining Walls?
- They are granite retaining walls laid in the tanizumi pattern in 1928 beside the penstock and around the main building. Together they run 68 metres and became a Registered Tangible Cultural Property in 2006.
- How are the Heisakubara Power Station Penstock and Main Building Retaining Walls laid out?
- There are two walls: a 17-metre wall beside the penstock and a 51-metre wall that bends around the west and north sides of the main building.
- What should I look for at the Heisakubara Power Station Penstock and Main Building Retaining Walls?
- Look at how the top line changes height to follow the ground, and at the diagonal pattern of the granite stones.
- Can I visit the Heisakubara Power Station Penstock and Main Building Retaining Walls?
- The exteriors can be viewed at any time free of charge, but the plant grounds and operational areas are closed.
- How do I get to the Heisakubara Power Station Penstock and Main Building Retaining Walls?
- The address is Heisakubara 1878, Kamisaibara, Kagamino Town. It is about 70 minutes by car from the Innoshō Interchange, or about 75 minutes by car from JR Innoshō Station.
Basic Information
| Name | Heisakubara Power Station Penstock and Main Building Retaining Walls |
|---|---|
| Location | Heisakubara 1878, Kamisaibara, Kagamino Town, Tomata District, Okayama Prefecture |
| Designation | Registered Tangible Cultural Property (Structure) |
| Year Designated | Registered 2006/11/29 (Heisei 18) |
| Quantity | 1 site |
| Dimensions | Total length 68 metres (penstock wall 17 metres, main building wall 51 metres) |
| Owner | Chugoku Electric Power Co., Inc. |
| Public Access | Exterior viewing only; grounds closed |
References
- Agency for Cultural Affairs, Database of National Cultural Properties: Heisakubara Power Station Penstock and Main Building Retaining Walls
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00006052
- Cultural Heritage Online: Heisakubara Power Station Penstock and Main Building Retaining Walls (Japanese)
- https://bunka.nii.ac.jp/heritages/detail/119127
- Agency for Cultural Affairs, Database of National Cultural Properties: Heisakubara Power Station Main Building
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00006051
- Chugoku Electric Power: History of Heisakubara Power Station (Japanese)
- https://www.energia.co.jp/isan/heisakubara_history.html
- Chugoku Electric Power: Heisakubara Power Station, Historic Electric Power Heritage (Japanese)
- https://www.energia.co.jp/isan/heisakubara.html
- Kagamino Town Tourism: Lake Onbara (Japanese)
- https://www.kagamino.holiday/spot/entry-322.html
Last verified: 2026.09.25
