Miroku Sekketsu: An Edo-Period Hand-Carved Water Tunnel
Hidden within the tranquil Miroku Natural Park in Sanuki City, Kagawa Prefecture, Miroku Sekketsu (弥勒石穴) stands as a remarkable testament to human determination and Edo-period engineering. This 189-meter irrigation tunnel was carved entirely by hand through solid rock between 1855 and 1857, driven by the desperate need to bring water to a drought-stricken agricultural community. Registered as a national Tangible Cultural Property in 2000, Miroku Sekketsu is a living piece of infrastructure that continues to channel water to this day — a rare example of pre-modern civil engineering still fulfilling its original purpose over 160 years later.
Historical Background: A Community's Struggle for Water
Kagawa Prefecture, located on the island of Shikoku, has long been known as one of Japan's driest regions. The Seto Inland Sea climate brings limited rainfall, making irrigation essential for rice cultivation and daily life. Miroku Pond (弥勒池) was improved in 1835 (Tenpō 6) to increase its water storage capacity, but for roughly 20 years after the renovation, the pond remained largely empty — described in local accounts as "a vessel with no water to fill it."
Determined to solve this chronic water shortage, the village headman Nokihara Shōzō (軒原庄蔵) petitioned the Takamatsu Domain in 1855 (Ansei 2) for permission to construct a rock tunnel that would channel water from Saiseki Valley (砕石谷), a tributary of the Tsuda River, into Miroku Pond. His petition was approved, and he was appointed as the official in charge of the tunneling project — given the title "Stone Tunnel Drilling Officer" (石穴掘抜方御用掛).
The Monumental Construction Effort
The engineering challenge was immense. Workers had to bore through Mitsuishi Mountain (三ツ石山) — a mass of solid rock — from both the east and west sides simultaneously. The entire excavation was accomplished using only hand chisels (手ノミ), with laborers working day and night in grueling conditions. The project was guided by the mathematical expertise of Hagiwara Eijirō (萩原栄次郎), a local scholar, while construction supervision was handled by Tada Shinzō (多田信蔵).
After three years of relentless effort, the tunnel was successfully completed in 1857 (Ansei 4), achieving a nearly straight bore of 189 to 191 meters in length. The tunnel's interior is just large enough for a person to walk through while crouching. The entrance portals were reinforced with cut stone and stone masonry retaining walls — construction details that remain visible today.
The success of Miroku Sekketsu brought Nokihara Shōzō great renown. In 1869 (Meiji 2), he was entrusted with an even more ambitious project: constructing the bottom sluice tunnel at Mannō Pond (満濃池), one of Japan's largest and most historically significant irrigation reservoirs, which had been damaged by the Ansei Earthquake.
Why Miroku Sekketsu Is a Registered Tangible Cultural Property
Miroku Sekketsu was registered as a national Tangible Cultural Property (登録有形文化財) on February 15, 2000. The designation recognizes its significance as a rare surviving example of an Edo-period hand-excavated irrigation tunnel. Key factors in the designation include the intact stone portal construction and masonry retaining walls at the tunnel entrance, the remarkable engineering achievement of boring through nearly 190 meters of solid rock using only manual tools, and the tunnel's continued use as a functioning part of the local irrigation system. The property is owned and maintained by the Tomida Central Water Users' Association (富田中央水利組合).
Highlights and What to See
Visitors to Miroku Sekketsu can observe the stone-reinforced tunnel entrance at the Miroku Pond side, where an information panel and a Registered Tangible Cultural Property plaque have been installed. The tunnel mouth, framed by carefully stacked stonework, offers a tangible connection to the Edo-period laborers who carved it. A memorial stone (記念碑) near the site commemorates the achievement.
The surrounding Miroku Natural Park provides a beautiful setting for the visit. Walking paths encircle Miroku Pond, and from the pond's embankment, visitors can look across to Tomida Chausuyama Kofun — the largest keyhole-shaped burial mound in all of Shikoku, designated as a National Historic Site. The juxtaposition of a 5th-century ancient tomb and a 19th-century irrigation tunnel in the same landscape powerfully illustrates the deep historical layers of this area.
Surrounding Attractions
The area around Miroku Sekketsu offers much more to explore. Miroku Natural Park itself features sports facilities, a field athletics course, camping grounds, log cabins, and the hot spring accommodation facility "Yū-topia Miroku." The Sanuki City History and Folklore Museum, located within the park, displays archaeological finds from the region including artifacts from Tomida Chausuyama Kofun — admission is just 100 yen for adults and 50 yen for children. The nearby Michi-no-Eki Miroku (Miroku Roadside Station) is a convenient stop for local produce and refreshments. For those exploring the wider region, the scenic Tsuda-no-Matsubara pine grove along the coast and the Shikoku Pilgrimage temple circuit are within easy reach.
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Q＆A
- Can visitors enter the tunnel?
- The tunnel interior is not open for public entry, as it remains an active water channel. However, the stone portal at the Miroku Pond side can be viewed up close, along with the information panel and cultural property plaque.
- Is there an admission fee?
- There is no admission fee to view Miroku Sekketsu. The site is located within Miroku Natural Park, which is free to enter and open year-round.
- How do I get to Miroku Sekketsu?
- By train, take the JR Kotoku Line to Sanuki-Tsuda Station and then a taxi for approximately 10 minutes. By car, exit the Takamatsu Expressway at Tsuda-Higashi IC, head west on Route 11 for about 2.5 km, then south on Prefectural Route 2 for approximately 3.5 km (about 15 minutes total).
- Is there English signage at the site?
- Signage at the tunnel site is primarily in Japanese. It is recommended to research the site's history in advance or bring a translation app. The nearby Sanuki City History and Folklore Museum may provide additional context.
- What is the best season to visit?
- Miroku Natural Park is enjoyable year-round. Spring brings cherry blossoms, autumn offers vibrant foliage, and the park's lush greenery is especially beautiful in early summer. The site is outdoors, so comfortable walking shoes are recommended.
Basic Information
| Name | Miroku Sekketsu (弥勒石穴) |
|---|---|
| Cultural Property Designation | Registered Tangible Cultural Property (Building) — Registered February 15, 2000 |
| Construction Period | Ansei 2–4 (1855–1857), Edo Period |
| Structure | Stone-built portal; tunnel length approximately 189 m |
| Key Figures | Designer: Nokihara Shōzō (village headman); Mathematical advisor: Hagiwara Eijirō; Construction supervisor: Tada Shinzō |
| Owner | Tomida Central Water Users' Association (富田中央水利組合) |
| Address | 3519-1 Ōkawa-chō Tomida-naka, Sanuki City, Kagawa Prefecture |
| Access | Approx. 10 min by taxi from JR Sanuki-Tsuda Station; approx. 15 min by car from Tsuda-Higashi IC (Takamatsu Expressway) |
| Admission | Free (located within Miroku Natural Park) |
References
- 弥勒石穴 — 文化遺産オンライン
- https://bunka.nii.ac.jp/heritages/detail/177756
- 弥勒石穴 — 農林水産省 水土里の文化遺産
- https://www.maff.go.jp/j/nousin/sekkei/museum/m_bunka/yuukei16/index.html
- 国指定文化財等データベース — 文化庁
- https://kunishitei.bunka.go.jp/bsys/maindetails/101/00001536
- 弥勒石穴 — じゃらんnet
- https://www.jalan.net/kankou/spt_37305ae2180022581/
- みろく自然公園 — うどん県旅ネット（香川県観光協会）
- https://www.my-kagawa.jp/point/211/
- 富田茶臼山古墳 — Wikipedia
- https://ja.wikipedia.org/wiki/%E5%AF%8C%E7%94%B0%E8%8C%B6%E8%87%BC%E5%B1%B1%E5%8F%A4%E5%A2%B3
Last verified: 2026.03.24