Matsusaka Tunnel

A Hundred-Year-Old Portal on the Pacific Coast of Shikoku

Tucked away on the wild southeastern coast of Tokushima Prefecture, where the Kuroshio Current polishes the shoreline of the Pacific Ocean and pilgrims have passed on foot for centuries, a short, unassuming concrete tunnel quietly holds a remarkable distinction. Matsusaka Tunnel (松坂隧道, Matsusaka Zuidō), completed in 1921, is recognized as the oldest surviving cast-in-place concrete road tunnel in Japan. For visitors who love discovering the understated history that the Japanese countryside holds in abundance, this modest 87-meter passage offers a rare chance to step inside a living artifact of modern industrial heritage — and, in early summer, to walk through a sea of hydrangeas that lead right up to its arched portal.

Historical Background: From Mountain Path to Modern Road

The coastline connecting Mugi Town to Asakawa was once considered one of the most difficult stretches of the Tosa Kaidō, the historic highway linking Tokushima with Kōchi. Travelers — including many of the pilgrims walking the 88-temple Shikoku Henro route — had to ascend a steep mountain pass called Matsusaka to continue southward along the coast. Local tradition tells of pilgrims clinging to vines (kazura) as they hauled themselves over the ridge, and a small shrine dedicated to Kōbō Daishi still stands quietly beside the tunnel entrance as a reminder of those arduous journeys.

In the early twentieth century, prefectural engineers set out to transform this difficult section of the coastal road. Construction on the broader road-improvement project began in 1914 (Taishō 3) and continued for eight years, ultimately costing 293,716 yen — an enormous sum at the time. The tunnel through Matsusaka Mountain itself was considered the most demanding part of the project. It was started in 1920 and completed in 1921, with the tunnel alone accounting for roughly one third of the total budget, or about 110,000 yen. When it opened, its 87-meter length, 5.8-meter width, and five-meter height represented a scale and a material choice that were nothing short of visionary for a rural coastal road.

Why It Was Designated a Cultural Property

Matsusaka Tunnel was registered as a National Registered Tangible Cultural Property (Structure) on September 10, 2010. Its significance lies less in grandeur than in pioneering technique. At the time of construction, concrete was still a relatively new and unfamiliar material in Japan, and most tunnels were built from cut stone or brick. Matsusaka Tunnel, by contrast, was built entirely of concrete poured in place on site — a method that required fresh engineering knowledge, purpose-built formwork, and skilled supervision in a remote coastal village.

An Architectural Snapshot of the Taishō Era

The tunnel is a straight shaft finished throughout in concrete, with a three-centered arch profile (三心円アーチ) whose gentle, slightly flattened curve was favored for early twentieth-century infrastructure. The portal and part of the lining are finished with a mortar surface, giving the entrances a refined, architectural appearance that goes beyond mere utility. Looking closely at the interior walls, visitors today can still see the small pebbles that surface within the concrete mix — a quiet witness to the experimental, still-developing concrete technology of the dawn of the Taishō era. The tunnel thus stands as a rare and well-preserved example of concrete tunnel construction from this formative period in Japanese civil engineering.

Highlights: What to Look For When You Visit

The Inscribed Portals: "The Road Passes Through Heaven and Earth"

Above the tunnel's two portals, look for chiseled inscriptions in elegant calligraphy. On one side, the characters read Matsusaka Zuidō — the tunnel's name. On the other side is the phrase Dō Tsū Ten Chi (道通天地), which can be translated as "the road passes through heaven and earth." Both were brushed by Ōtsu Rinpei, who served as the 27th Governor of Tokushima from April 1919 to May 1921. For travelers who had previously climbed Matsusaka Pass on foot, the straight, level road through the tunnel must truly have felt like a shortcut between worlds.

Traces of Original Red Paint

The wing walls flanking the portals once carried a red coat of paint. On the east-facing side, patches of that original color still linger faintly, while the sunnier south side has weathered more. These subtle color differences remind us that this was, in its day, not a forgotten back road but a proud piece of prefectural infrastructure.

A Small Shrine to Kōbō Daishi

Just beside the Tokushima-side entrance stands a small stone shrine dedicated to Kōbō Daishi (Kūkai), founder of Shingon Buddhism and the figure at the heart of Shikoku's 88-temple pilgrimage. It is a quiet reminder that this coastline was — and still is — walked by white-clad pilgrims, and that the tunnel eased their journey as much as it did that of carriages and, later, automobiles.

A Retired Main Road, Now a Cinematic Lane

National Route 55 has long since moved to a newer alignment, leaving the old road (now a town road) remarkably quiet. Walking or cycling through the tunnel feels cinematic — a frame from an old film, with the arched portal opening onto mountain greenery on one side and a glimpse of the blue Pacific on the other.

Around the Tunnel: The Uchizuma Hydrangea Road

The approach to Matsusaka Tunnel is arguably as memorable as the tunnel itself. Along roughly two kilometers of the old national road surrounding Uchizuma Beach, about 4,000 hydrangea plants have been lovingly cultivated by the local community, earning the lane the nickname Uchizuma Hydrangea Road (内妻あじさいロード). From early June to early July, and especially in mid- to late June, the road becomes a ribbon of blue, violet, and rose framing the gray-white concrete of the tunnel portal.

Every June, the Uchizuma Hydrangea Festival (内妻あじさいまつり) is held along this stretch, organized by the local residents' committee and supported by the town of Mugi. Stalls offer yakisoba, fried octopus, grilled skewers and other local favorites, and visitors can take home hydrangea seedlings to plant in their own gardens. Inside the tunnel itself, a special andon (paper lantern) exhibition is held during the festival, softly illuminating the historic concrete walls — a scene that residents sometimes liken to a quiet corner from a Studio Ghibli film.

Visitor Information and Access

Matsusaka Tunnel is open-air and freely accessible to the public at any time of day. There is no admission fee and no ticket counter. Visitors should be aware that it remains an active town road: cars still occasionally pass through, so walkers are asked to stay mindful of traffic, particularly in wet weather or at dusk.

Getting There

• By train and taxi: Take the JR Mugi Line to Mugi Station. From there, a taxi ride of about 5–10 minutes heading southwest toward Muroto leads to the Uchizuma area.
• By car from Tokushima City: Head south on National Route 55 for about 1 hour 50 minutes to Uchizuma Beach, then turn onto the old Route 55 (now a town road) and drive about 3 minutes to reach the tunnel.
• By bicycle: The old road is paved, gently curved, and largely free of traffic, making it a rewarding detour for cyclists traveling the southern Tokushima coast.

When to Visit

The tunnel can be visited year-round, but two seasons stand out. Mid- to late June, during the hydrangea bloom, is the most photogenic moment and coincides with the local festival. The summer months of July and August bring warm swimming and surfing weather to nearby Uchizuma Beach. In autumn, the surrounding mountains take on rich colors, and on clear winter days the Pacific gleams with deep blue intensity.

Nearby Attractions

Mugi Town and its neighbors along the Muroto-Anan Coast Quasi-National Park reward travelers who plan at least a full day in the area.

Uchizuma Beach (内妻海岸)

A small, south-facing cove of soft sand and clear water located only minutes from the tunnel. It is known across Japan as a surf spot, with a local surfing culture dating back to the late 1970s. Even non-surfers enjoy the view of pines, sand, and the Pacific at sunset.

Teba Island (出羽島)

A 15-minute ferry ride from Mugi Port brings you to this tiny island, designated as an Important Preservation District for Groups of Traditional Buildings in 2017. Cars are not allowed, the narrow lanes called awae weave between wooden houses, and the island is the only native habitat in Japan of the aquatic plant shiratamamo, a Natural Monument.

Morasco Mugi (モラスコむぎ)

A community complex on the Mugi coast that houses the Museum of Shells, displaying about 6,000 shell and fossil specimens from around the world. It also offers co-working space and a seaside lounge — a pleasant stop for rainy-day exploration.

Yasaka-Yahama Coast (八坂八浜)

The name refers to "eight slopes and eight beaches," a beautifully varied stretch of coastline running through Mugi and Kaiyō. The old road that Matsusaka Tunnel pierces was originally built to tame this very section of the coast.

Yakuō-ji Temple (薬王寺)

Approximately 15 kilometers north in the town of Hiwasa, this is the 23rd temple of the 88-temple Shikoku Pilgrimage. Its vermilion pagoda and hillside grounds make it a well-loved stop for both pilgrims and sightseers.