A Concrete Arch Over the Upper Chikuma River
In the southern Saku basin of Nagano, a single concrete arch leaps across the upper reaches of the Chikuma River with a clear span of 45 meters. This is Sakae Bridge, finished in 1938 and still carrying a quiet prefectural road over the water at Takanomachi in Sakuho Town. The arch is not steel, as most arches of this scale would have been at the time, but reinforced concrete cast into a flattened parabolic curve. It holds a particular record: among the concrete arch bridges built in Japan before the Second World War, no span of its type reaches farther.
The full structure measures 86.72 meters from bank to bank and 6 meters across, registered in the national database as roughly 87 meters long. The Lohse arch sits at the center. On either side, shorter girder sections reach out to meet it through cantilevered joints, so the bridge reads as three spans working together rather than one. A Lohse bridge is a form in which the curved arch and the horizontal deck beam are both built stiff, sharing the bending forces between them instead of leaving the load to one member alone. The road runs through the arch rather than over the top of it, which is why a driver crossing today passes beneath the rising curve of concrete.
The name comes from Sakae, a village in the old Minamisaku district that has since been absorbed into Sakuho Town. A first bridge stood here long before the concrete one. In November 1891 a timber crossing 104 meters long and only 1.8 meters wide spanned the same stretch of river, a reminder of how narrow rural roads once were before motor traffic arrived.
The Engineer Behind the Form
Sakae Bridge belongs to a small family of structures that grew from one engineer's idea. Nakajima Takeshi (1906 to 1980), born in Sapporo and trained in civil engineering at Hokkaido Imperial University, arrived in Nagano as a prefectural road engineer in 1933. He stayed only about three and a half years before moving on to Niigata, yet in that short window he designed seven concrete Lohse bridges, said to be the first of their kind anywhere in the world.
The reason was scarcity. As Japan moved toward a wartime footing, steel grew hard to obtain, and bridges already planned in steel had to be rethought. Nakajima had published structural studies of Langer, Lohse, and Vierendeel girders during his earlier years in Gifu, and he saw a way to recast the steel Lohse form in concrete. The problem lay at the joint. In a steel Lohse bridge the arch meets the girder through a hinge; concrete cannot easily form a working hinge, so Nakajima made the connection rigid instead, worked out a simplified way to calculate the resulting "modified Lohse girder," and turned the idea into a buildable standard. His first concrete Lohse bridge, Ote Bridge in Kiso, opened in 1936 with a 35-meter span. He later recalled how long that span felt at the moment the temporary supports came away.
Sakae Bridge, two years later, pushed the span to 45 meters, the largest of the group. For decades Nakajima's role went unrecorded, since the designers of civil structures rarely had their names attached to them. His authorship was recovered through research led by Konishi Junichi of Shinshu University. In 2002 five of his surviving bridges, Ote, Himekawa, Oyazawa, Showa, and Sakae, were recognized together by the Japan Society of Civil Engineers as Selected Civil Engineering Heritage. In March 2025 Sakae Bridge was entered on the national list of Registered Tangible Cultural Properties, cited as a work that sets a model for its design.
What to Look For at the Bridge
The first thing most visitors notice is not the arch but the gateposts. Four large parapet posts, two at each end, rise well above the railing in a tapering, pointed shape faced with stone. The design borrows the motif of a Gothic spire, and these posts count among the tallest of their kind in the prefecture. Seen from the approach road they stand like sentries marking the entry to the crossing.
To take in the arch itself, walk down toward the riverbank and look back at the bridge from the side. From there the parabola reads clearly, and the way the central arch hands off to the flanking girders becomes legible. Winter rewards the patient visitor: with the trees bare and the sky often a hard blue, the pale concrete shows its weight and the posts cut sharp silhouettes against the cold air.
The bridge carries a working prefectural road and stands in the open, so there is no gate, no ticket, and no fixed hours. It can be seen and crossed freely at any time of year. As you cross on foot, the rhythm of the structure under the road surface, central span flanked by cantilevered ends, is something you feel as much as see.
Around Sakuho Town
Sakae Bridge sits along the route that once linked the Saku-Koshu road, now National Route 141, with the Bushu road, National Route 299, by way of Haguroshita Station on the Koumi Line. That same Route 299 climbs west into the Yatsugatake mountains as the Mervogen Highway, a drive that grows more beautiful as it rises into highland forest.
High above the town lies Shirakoma Pond, a lake set above 2,000 meters in the northern Yatsugatake range and ringed by one of Japan's notable old-growth forests. The forest floor here is carpeted in mosses recognized among the country's finest, and a boardwalk lets walkers move through the green hush without disturbing it. Autumn turns the surrounding slopes deep red. Closer to the valley, the Yachiho Highland is known for its white birch groves and a large nature park that opens for the warm months.
The Koumi Line that passes through Sakuho is itself worth a mention. Running along the high spine between the Saku basin and the Yatsugatake foothills, it reaches some of the highest railway elevations in Japan, and a slow local train makes an easy and scenic way to approach the area.
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Q&A
- Can I visit and cross Sakae Bridge freely?
- Yes. It carries an active prefectural road and is open to the public at all times, with no admission or set hours. Take ordinary care, as it is a road shared with vehicles.
- What makes this bridge worth a special trip?
- It is the longest-span concrete Lohse arch bridge built in Japan before the war, at 45 meters, and one of only five surviving works by the engineer who pioneered the form, Nakajima Takeshi. The tall stone-faced parapet posts are a distinctive sight.
- What is a Lohse bridge?
- It is an arch bridge in which both the arch and the horizontal deck beam are made stiff so they share the bending load. The road passes through the arch. Nakajima adapted the form, originally used in steel, to reinforced concrete.
- How do I get there by public transport?
- The nearest station is Haguroshita on the JR Koumi Line, from which the bridge is a short taxi ride. By car, the Saku-Minami interchange on the Chubu-Odan Expressway is about a 50-minute drive away.
- When is the best time to see it?
- The bridge can be viewed year-round. Clear winter days show the concrete form and parapet posts at their starkest, while combining the visit with Shirakoma Pond suits late spring through autumn, when the highland road and forest are open.
Basic Information
| Name | Sakae Bridge (Sakaehashi) |
|---|---|
| Location | Takanomachi, Sakuho Town, Minamisaku District, Nagano Prefecture |
| Designation | Registered Tangible Cultural Property (Structures), registration no. 20-0667 |
| Registered | 13 March 2025 |
| Built | 1938 (Showa 13) |
| Designer | Nakajima Takeshi |
| Structure | Reinforced-concrete Lohse girder bridge with cantilevered side spans; length approx. 87 m (86.72 m), width 6.0 m, central span 45 m, with parapet posts |
| Quantity | 1 structure |
| Owner | Nagano Prefecture |
| Access | Short taxi ride from Haguroshita Station, JR Koumi Line; open to the public at all times |
References
- National Database of Designated Cultural Properties, Agency for Cultural Affairs: Sakae Bridge
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00015313
- Cultural Heritage Online (National Institutes for Cultural Heritage): Sakae Bridge
- https://bunka.nii.ac.jp/heritages/detail/544527
- Japan Society of Civil Engineers, Selected Civil Engineering Heritage: Concrete Lohse Girders Designed by Nakajima Takeshi
- https://committees.jsce.or.jp/heritage/node/226
- Sakuho Town Tourism Association
- https://yachiho-kogen.jp/
Last verified: 2026.06.20