A Concrete Bore That Bends and Climbs
The Kominato Railway Tsukizaki First Tunnel (小湊鉄道月崎第一隧道, Tsukizaki Dai-ichi Zuidō) is a concrete railway tunnel built around 1926 in the Kakinokidai district of Ichihara City, Chiba Prefecture, and was registered as a Registered Tangible Cultural Property on May 2, 2017.
The Kominato Railway Tsukizaki First Tunnel lies about 3 kilometers south of Satomi on the second section of the line, between Satomi and Tsukizaki, which opened on September 1, 1926.
Changing Course and Gradient
The Agency for Cultural Affairs records it as a concrete tunnel 135 meters long and 3.8 meters wide.
In plan it curves like a drawn bow, and partway through, the gradient changes from 1 in 88 to 1 in 330. The agency describes it as a structure whose shape shifts in three dimensions.
It is also cast entirely in place, poured into formwork on site, unlike the later Okubo and Itaya tunnels, whose arches are built of concrete blocks.
Seeing It
The Kominato Railway Tsukizaki First Tunnel is part of a working line and cannot be entered. In normal times the surest way to experience it is from a train window, feeling the curve and change of grade. If you look at a portal from outside, stay off the track and private land.
Since Typhoon No. 25 struck in September 2026, the line between Kazusa Ushiku and Kazusa-Nakano has been suspended until further notice, with no replacement buses (company statement of September 24, 2026), so for now it cannot be reached by train.
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Q&A
- When was the Kominato Railway Tsukizaki First Tunnel built?
- Around 1926, according to the Agency for Cultural Affairs.
- How long is the Tsukizaki First Tunnel?
- 135 meters long and 3.8 meters wide.
- What is unusual about the Kominato Railway Tsukizaki First Tunnel?
- It curves in plan, changes gradient from 1 in 88 to 1 in 330, and is cast entirely in situ.
- Can I walk through the Tsukizaki First Tunnel?
- No. It is on a working line; ride through it on a train instead.
- Can I travel through the tunnel now?
- Not at present. The line beyond Kazusa Ushiku has been suspended since typhoon damage in September 2026.
Basic Information
| Name | Kominato Railway Tsukizaki First Tunnel (小湊鉄道月崎第一隧道) |
|---|---|
| Location | 628-3 Koido to 803-3 Hochi, Kakinokidai, Ichihara City, Chiba Prefecture |
| Designation | Registered Tangible Cultural Property (Structure) |
| Year Designated | Registered 2017/5/2 (Heisei 29) |
| Quantity | 1 structure |
| Dimensions | Concrete, 135 meters long, 3.8 meters wide |
| Owner | Kominato Railway Co., Ltd. |
| Public Access | Working line; no access (section suspended after 2026 typhoon damage) |
References
- Agency for Cultural Affairs, Database of National Cultural Properties: 小湊鉄道月崎第一隧道
- https://kunishitei.bunka.go.jp/heritage/detail/101/00011473
- Cultural Heritage Online: 小湊鉄道月崎第一隧道
- https://online.bunka.go.jp/heritages/detail/300449
- Kominato Railway: 22 facilities registered as Registered Tangible Cultural Properties (Japanese)
- https://www.kominato.co.jp/corporate/topics/heritage/index.html
- Kominato Railway: Damage from Typhoon No. 25 and recovery outlook, September 24, 2026 (Japanese)
- https://www.kominato.co.jp/wp-content/uploads/2026/09/30216b45daba750194c363de3f54800f.pdf
Last verified: 2026.10.01
