A portal hidden behind its own defences
The Watarase Keikoku Railway Nagoshi Tunnel is a single-track railway tunnel of 1912 at Sori in Higashimachi, Midori City, Gunma Prefecture, listed as a Registered Tangible Cultural Property in 2009. It runs 32 metres on a gentle curve. Stone is used for the side walls, brick for the arch, and the portals are stone throughout, arch included.
Its cross section is worth noting. The Agency for Cultural Affairs describes it as a horseshoe closer to a full circle than the standard design used by the government railways of the day. A horseshoe makes sense for taking load from above, and the departure from the standard points to something particular about the ground here or the way the work was carried out.
Seeing the portal from a train is another matter. Rockfall sheds cover both entrances to protect the track and the bore, so the Taisho era stonework sits behind them. The oldest of these sheds dates from 1936 and more was added in 1979. Some of the posts holding them up are lengths of worn out rail put back to work.
North of Sori, where the gorge tightens
The Watarase Keikoku Railway Nagoshi Tunnel belongs to the stretch north of Sori where the valley narrows and deepens. The Ashio Railway opened the section between Godo and Sori in November 1912 and pushed on from Sori to Ashio in December of the same year. This bore was driven during that push. Sori Station lies about 1,050 metres to the southwest, and the Yoshinozawa Aqueduct about 1,400 metres to the north.
The line's structures were registered on 2 November 2009, with public notice on the 19th, when 38 works between Kiryu and Mato were listed together. It was the first time a complete Japanese railway line had been listed across two prefectures, under the criterion of contribution to the historic landscape of the country, and in 2016 the group was named a Civil Engineering Heritage. That a bore of 1912 still carries trains, patched with later rockfall sheds, is precisely the kind of survival the registration system is meant to recognise.
A short darkness, and the slopes on either side
Thirty-two metres passes in a blink. With the Watarase Keikoku Railway Nagoshi Tunnel the interest lies less in the dark than in what frames it. Light comes through the rockfall sheds in narrow bars, and beyond the far end the hillside stands close and steep. That the sheds have been extended twice tells you how much this slope has moved.
Heading from Sori towards Mato the tunnel appears about two minutes out; coming the other way from Harumukai towards Kiryu it takes roughly six and a half minutes. The operator's leaflet says the reused rail is in the shed on the Sori side while Midori City places it on the Ashio side. Either way, look at the posts and some of them turn out to have the profile of a rail.
Visiting
The Watarase Keikoku Railway Nagoshi Tunnel is on live track, closed to entry and to pedestrians, so it is seen from trains between Sori and Harumukai. Sori is an unstaffed station that keeps a platform of 1912 and a waiting room of the late 1920s, and its hydrangeas are at their best in July. Riding out and back from there takes in the Nagoshi Tunnel, the Yoshinozawa Aqueduct and the long Kasamatsu Tunnel in one go.
Torokko trains need a seat coupon in addition to the fare, 700 yen for adults and 350 yen for children from 1 September 2026, and they fill up in high season. A one day free pass is 1,880 yen for adults and 940 yen for children. Photography from the carriage is unrestricted, but drone filming of trains and the track area is prohibited. Check operating days on the company website; fares here were confirmed on 13 September 2026.
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Q&A
- How is the name of the Watarase Keikoku Railway Nagoshi Tunnel read?
- Nagoshi. The reading is given in the phonetic field of the Agency for Cultural Affairs database, which spells it out as watarase keikoku tetsudo nagoshi tonneru.
- How long is the Watarase Keikoku Railway Nagoshi Tunnel?
- 32 metres, single track and gently curved, with stone side walls, a brick arch and portals built entirely of stone.
- Can the portals of the Watarase Keikoku Railway Nagoshi Tunnel be seen from the train?
- Barely. Rockfall sheds cover both entrances. The oldest dates from 1936, with further work in 1979.
- Which stations flank the Watarase Keikoku Railway Nagoshi Tunnel?
- Sori and Harumukai. It appears about two minutes north of Sori, or about six and a half minutes from Harumukai heading towards Kiryu.
- What is unusual about the section of the Watarase Keikoku Railway Nagoshi Tunnel?
- It is a horseshoe closer to a circle than the standard government railway design of the period, a form chosen to take the load from above.
Basic Information
| Name | Watarase Keikoku Railway Nagoshi Tunnel |
|---|---|
| Location | Sori, Higashimachi, Midori City, Gunma Prefecture |
| Designation | Registered Tangible Cultural Property (structure) |
| Year Designated | Registered in 2009 (Heisei 21) |
| Quantity | 1 structure |
| Dimensions | Length 32 metres |
| Owner | Not recorded in the Agency for Cultural Affairs database; the line is operated by Watarase Keikoku Railway Co., Ltd. |
| Public Access | Not open to entry; seen from passing trains |
References
- Agency for Cultural Affairs, National Cultural Properties Database: Watarase Keikoku Railway Nagoshi Tunnel
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00007852
- Midori City: Nagoshi Tunnel
- https://www.city.midori.gunma.jp/kosodate/1001647/1001800/1002430/1002478.html
- Watarase Keikoku Railway Co., Ltd.: cultural property leaflet
- https://www.watetsu.com/assets/pdf/sightseeing/culture_yukei_des05.pdf
- Watarase Keikoku Railway Co., Ltd.: Torokko Watarase Keikoku train
- https://www.watetsu.com/train/torokei.php
Last verified: 2026.09.13