A River Connected to the Kumano Kodo
The Tonda River also has a deep connection with the Kumano Kodo pilgrimage routes. Historic paths associated with the Nakahechi and Ohechi routes pass through the river basin, while former pilgrimage sites, shrines, and sacred places can be found throughout the surrounding area.
For centuries, nature, religious traditions, and everyday life have developed together along the Tonda River. Walking through the river basin therefore offers more than beautiful scenery—it provides an opportunity to discover the cultural landscape that developed around the pilgrimage routes to Kumano.
The Appeal of a River Without Dams
The Tonda River is known for its exceptionally clear water. Much of its watershed is covered by forest, helping maintain the river’s clean and healthy environment.
The river supports a variety of aquatic life, including ayu sweetfish, amago trout, and yamame trout. Freshwater shrimp and Japanese mitten crabs can also be found in the river, demonstrating the richness of its ecosystem.
In the lower reaches, the river is also associated with habitats of the giant mottled eel, a nationally designated Natural Monument of Japan. Its presence reflects the ecological connection between the river and the ocean.
The scenery changes beautifully with the seasons. Fresh green foliage appears in spring, summer brings the traditional sight of ayu fishing, autumn colors the surrounding mountains, and winter creates a crisp, peaceful atmosphere along the water.
The Unique Submersible Bridges of the Tonda River
Bridges Designed to Disappear Beneath the Water
One of the most distinctive features of the Tonda River is its submersible bridges, known in Japan as sensui-kyō or, more commonly, chin-ka-kyō. In Kamitonda, the term “submersible bridge” is especially familiar.
The most noticeable characteristic of these bridges is their lack of railings. During floods, floating logs and other debris can become trapped against railings and cause serious damage. By keeping the bridge surface open, the design allows floodwater and debris to pass over the structure more easily.
The Tonda River has historically been prone to flooding and was once regarded as a particularly powerful and unpredictable river. These unusual bridges represent a practical example of how local communities adapted to the natural environment rather than attempting to completely control it.
Sanno Bridge: A Thrilling Walk Above the River
Among the submersible bridges along the Tonda River, Sanno Bridge in Ikuma, Kamitonda, is particularly well known.
The bridge is extremely narrow, with barely enough space for two people to pass each other. There are no handrails on either side, bringing visitors remarkably close to the water below. Walking across can create the unusual sensation of almost walking directly on the surface of the river.
The current bridge is made of concrete, but earlier versions were wooden. They were repeatedly washed away by floods. The structure was subsequently improved using ideas inspired by the famous submerged bridges of the Shimanto River in Kochi Prefecture.
Further improvements were made during the Showa period, including strengthening the bridge piers and extending the bridge to create the structure seen today.
Surrounded by traditional rice fields and rural scenery, Sanno Bridge offers a glimpse of a quieter side of Japan. Its narrow shape, open design, and beautiful natural surroundings have also made it a popular destination for photographers.
Hatayama Bridge: Another Scenic Submersible Bridge
Another notable submersible bridge in Kamitonda is Hatayama Bridge. Connecting the Iwata and Ichinose areas, the bridge stretches for approximately 174 meters while being only about 1.5 meters wide.
Like Sanno Bridge, it is close to the water and has no conventional railings, giving visitors a strong sense of being immersed in the river landscape.
The surrounding area also contains historic sites associated with the Kumano Kodo, including the former sites of Inabane-oji and Yagami-oji. Visiting the bridge as part of a pilgrimage-route walk allows travelers to combine natural scenery with the history of Kumano.
Yūbin Bridge: A Bridge with a Remarkable Name
A Bridge Born from Japan’s Early Postal System
The Tonda River is also home to a bridge with one of the most unusual names in Japan: Yūbin Bridge, literally meaning “Post Bridge.”
The name dates back to the beginning of Japan’s modern postal system. Japan introduced its national postal service in 1871, and postal facilities were established in the Kinan region soon afterward.
At the time, several ferry crossings operated along the Tonda River. One ferry was specially operated under prefectural management to help transport mail.
According to local stories, when a postal worker carrying a mailbag was seen approaching the river, a ferry that had already departed for the opposite bank would sometimes turn around and return to pick up the mail carrier.
Eventually, the ferries were discontinued and simple plank bridges were constructed. Local people began calling one of these crossings Yūbin Kobashi, or “Little Post Bridge.” When a larger bridge was later built, the name was shortened to Yūbin Bridge.
A Bridge Rebuilt Again and Again
Like many structures along the Tonda River, Yūbin Bridge has repeatedly suffered damage from floods. Its early forms included plank and wooden bridges, which were later replaced by stronger iron and concrete structures during the modern era.
The present bridge provides an important transportation link for the local community while preserving the unusual name that recalls the early days of Japan’s postal service.
A postal symbol monument and an object depicting a boy carrying mail have also been placed near the bridge. These features help visitors understand the story behind its distinctive name.
Scenic Highlights Along the Tonda River
Fukusada’s Great Ginkgo Tree
One of the most impressive seasonal sights in the Tonda River basin is the Great Ginkgo Tree of Fukusada, located in Fukusada, Nakahechi-cho, Tanabe.
Standing within the grounds of Hosenji Temple, this magnificent tree is estimated to be approximately 400 years old. It rises around 22 meters high and has a trunk circumference of approximately 5.3 meters.
In autumn, the entire tree turns a brilliant golden yellow, standing out dramatically against the surrounding mountain landscape. Its impressive appearance has earned it the nickname “Senbon Ginkgo”, referring to its many branches and the spectacular impression created by its crown.
The trunk divides into several large sections, revealing the strength of a tree that has survived for centuries. The marks and scars accumulated over its long life add to its character and beauty.
During the autumn foliage season, the tree attracts photographers and visitors, and it is often enjoyed as part of a journey along the historic Kumano Kodo.
Where Nature and History Come Together
The Tonda River is much more than a waterway. Its landscape tells the story of the Kumano Kodo, local communities, traditional ways of life, and people’s long relationship with nature.
The unusual submersible bridges and Yūbin Bridge are especially fascinating because they preserve stories that cannot be understood simply by looking at the river itself. They reveal how generations of local people adapted their lives to the river and incorporated it into transportation, communication, agriculture, and everyday life.
At the same time, the clear water, forests, wildlife, rice fields, and seasonal scenery provide an opportunity to experience the peaceful natural beauty of southern Wakayama.
For travelers exploring the Kumano Kodo and the Kii Peninsula, taking time to explore the Tonda River basin offers a different perspective on the region—one where history and spirituality are woven into an unspoiled rural landscape.
Experience the Peaceful Landscape of Southern Wakayama
Whether you are interested in Japanese history, pilgrimage routes, traditional engineering, photography, wildlife, or simply beautiful landscapes, the Tonda River offers many ways to enjoy the region.
Take a quiet walk beside the river, cross one of its distinctive bridges, discover historic sites along the Kumano Kodo, or admire the magnificent autumn colors of the Great Ginkgo Tree of Fukusada.
The Tonda River is a place where the natural beauty of the Kii Peninsula and the history of the people who have lived alongside it continue to exist together.