The Longest Tunnel of the Ashio Railway
The Watarase Keikoku Railway Kasamatsu Tunnel (わたらせ渓谷鐵道笠松トンネル) is a single-track brick and stone tunnel built in 1912 at the boundary of Ashio-machi, Nikko City, Tochigi Prefecture, and Azuma-cho, Midori City, Gunma Prefecture, and was registered as a Registered Tangible Cultural Property (structure) on November 2, 2009 (Agency for Cultural Affairs).
The Agency for Cultural Affairs records brick and stone, 362 metres long, registration number 09-0189.
The Ashio Copper Railway
According to Watarase Keikoku Railway, the Ashio copper mine, bought by Furukawa Ichibei in 1877, grew to produce half of Japan's copper, more than horses and a horse tramway could carry, so a railway was built from Kiryu to Ashio. The Ashio Railway opened to Omama in 1911, reached Ashio in December 1912 and was completed to Ashio Honzan in 1914. Nationalised in 1918 as the Ashio Line, it has been run by Watarase Keikoku Railway since 1989.
The Watarase Keikoku Railway Kasamatsu Tunnel lies about 2,800 metres south-west of the Second Watarase River Bridge and runs across the Gunma-Tochigi border (Agency for Cultural Affairs).
Value as a Registered Cultural Property
The Watarase Keikoku Railway Kasamatsu Tunnel was registered as a structure contributing to the historic landscape of the country. According to Watarase Keikoku Railway, it is the longest tunnel built for the Ashio Railway.
What to Look For
The Agency for Cultural Affairs describes a gently curving 362-metre single-track tunnel with a horseshoe section based on a single-centred arch, stone side walls, a brick arch four bricks thick and six refuges inside.
Watarase Keikoku Railway's pamphlet notes that the portals of the Watarase Keikoku Railway Kasamatsu Tunnel have brick arches over dressed stone walls.
Visiting
The Watarase Keikoku Railway Kasamatsu Tunnel comes into view about five and a half minutes after Sori Station on a Mato-bound train, or about two minutes after Haramuko Station on a Kiryu-bound train (Watarase Keikoku Railway). Watarase Keikoku Railway notes that all of its registered structures can be seen from the train.
Do not enter the tracks; view it from the train, the station or nearby roads. It is located at Ashio-machi, Nikko City, Tochigi Prefecture, and Sori, Azuma-cho, Midori City, Gunma Prefecture. Of the line's 38 registered structures, the 26 in Gunma and 11 in Tochigi are gathered on the group pages Watarase Keikoku Railway (Gunma Section) and Watarase Keikoku Railway (Tochigi Section).
- 📍 Plan Your Visit to Tochigi
- Find tours, activities & transport passes near Watarase Keikoku Railway Kasamatsu Tunnel
- [ Nikko Toshogu Shrine & Kegon Falls Day Trip ]
Q&A
- When was it built?
- In 1912 (Agency for Cultural Affairs).
- How is it built?
- Brick and stone, 362 metres long (Agency for Cultural Affairs).
- What is inside?
- Six refuges for track workers (Agency for Cultural Affairs).
- Where can it be seen?
- The Watarase Keikoku Railway Kasamatsu Tunnel comes into view about five and a half minutes after Sori Station on a Mato-bound train, or about two minutes after Haramuko Station on a Kiryu-bound train (Watarase Keikoku Railway).
- When was the Watarase Keikoku Railway Kasamatsu Tunnel registered?
- On November 2, 2009.
Basic Information
| Name | Watarase Keikoku Railway Kasamatsu Tunnel (わたらせ渓谷鐵道笠松トンネル) |
|---|---|
| Location | Ashio-machi, Nikko City, Tochigi Prefecture, and Sori, Azuma-cho, Midori City, Gunma Prefecture |
| Designation | Registered Tangible Cultural Property (Structure) |
| Year Designated | Registered 2009/11/02 (Heisei 21) |
| Quantity | 1 structure |
| Dimensions | Brick and stone, length 362 metres |
| Owner | Not listed in the national database (line operated by Watarase Keikoku Railway Co., Ltd.) |
| Public Access | Visible from the train |
References
- Watarase Keikoku Railway Kasamatsu Tunnel (Database of National Cultural Properties, Agency for Cultural Affairs)
- https://kunishitei.bunka.go.jp/heritage/detail/101/00007850
- Registered Tangible Cultural Properties (Watarase Keikoku Railway, in Japanese)
- https://www.watetsu.com/sightseeing/culture.php
- Pamphlet: Railway Heritage from the Train Window, map notes (Watarase Keikoku Railway, in Japanese)
- https://www.watetsu.com/assets/pdf/sightseeing/culture_yukei_des05.pdf
- History (Watarase Keikoku Railway, in Japanese)
- https://www.watetsu.com/company/history.php
Last verified: 2026.10.12