Watarase Keikoku Railway Second Kanbai Tunnel

The least altered bore on the line

The Watarase Keikoku Railway Second Kanbai Tunnel is a single-track railway tunnel of 1912 at Shimokanbai in Omama, Midori City, Gunma Prefecture, and it was listed as a Registered Tangible Cultural Property in 2009. It runs straight for 27 metres. The lining is brick throughout; Midori City describes English bond in the side walls and stretcher bond overhead, with no cut stone used inside at all. Of the nine tunnels on the Watarase Keikoku Line, this is the one held to preserve most of its original fabric.

The portal brickwork is four courses thick. The keystone at the crown of the arch is finished in the edo-giri manner, its margins pared back so the block reads as a distinct shape against the brick. The two portals differ from each other in how their stone is coursed, and on the northern side a 7.7 metre retaining wall in valley bond carries on holding the slope. Later intervention amounts to sprayed concrete against water seepage and an addition made in 1925.

The Agency for Cultural Affairs record dates that addition to Taisho 14 but prints 1939 beside it. Taisho 14 corresponds to 1925.

Three bores through the Seven Bends

Where the Watarase River has undercut the hillside between Kirihara and Shimokanbai, cliffs press close to the track. The old copper road called this stretch Nanamagari, the Seven Bends, and the Ashio Railway, built to bring ore down from the Ashio copper mine, cut three tunnels to get through it. The Watarase Keikoku Railway Second Kanbai Tunnel is the middle one, about 90 metres from the Third to the northwest and some 240 metres from the First to the southeast.

The line was nationalised in 1918, lost most of its traffic when the mine closed in 1973, and passed to a third sector company in 1989. On 2 November 2009, with public notice on the 19th, 38 structures between Kiryu and Mato were listed together as Registered Tangible Cultural Properties, the first time in Japan that a whole line's works had been listed across two prefectures. The group was recognised as a Civil Engineering Heritage in 2016, and the operator lists the Second Kanbai Tunnel among the places worth watching for from the window.

Twenty-seven metres, and what to look at

Twenty-seven metres passes in a few seconds. Even so, the Watarase Keikoku Railway Second Kanbai Tunnel repays a look at its portal as the train comes up to it. The keystone sits in the arch with a slightly different shadow line from the brick around it, the mark of that pared finish. Then the stonework of the far portal turns out to be coursed another way entirely.

Late autumn and winter show it best. Once the slope loses its leaves, the portal and the retaining wall stand clear instead of half hidden in green. Because the three bores follow one another so closely, the ride through here becomes a rhythm of dark, light, dark again.

Visiting

The Watarase Keikoku Railway Second Kanbai Tunnel carries live track, so there is no walking in and no access to the track area. It is seen from trains running between Omama and Kamikanbai. In an open sided Torokko carriage the portal feels close enough to touch. Two such trains run, the Torokko Watarase Keikoku and the Torokko Wasshi, and both require a Torokko seat coupon on top of the ordinary fare, set from 1 September 2026 at 700 yen for adults and 350 yen for children. Seats sell out on busy days, so reserve by phone or through the website.

To see several of the listed structures in one go, the one day free pass costs 1,880 yen for adults and 940 yen for children. Photography from inside the carriage is fine; drone filming of the track area and of trains is banned outright. Ticket details are on the company website, and the fares given here were checked on 13 September 2026.