Guide
Mukiyama Tunnel is an unlined tunnel approximately 110m long, located in Otaki, Chiba Prefecture. The most remarkable feature of this site is its unique structure. Because a new tunnel was excavated beneath the original upper tunnel, it possesses a rare double-layered formation. The Kyoei Tunnel lies to the west, while Mukiyama Tunnel is situated to the east. The raw, unlined texture of the exposed rock creates a distinctive landscape that differs significantly from modern, man-made concrete structures.
This tunnel carries a history of two-stage construction as part of the region's transportation infrastructure. The current double-layered structure was completed through a process of creating a new path while preserving the original upper structure. The unlined method used reflects the geological conditions and the engineering techniques of the time. The fact that this raw, unlined structure remains—standing in stark contrast to modern concrete tunnels—tells the story of the region's infrastructural evolution.
The primary highlight is undoubtedly the "double-layered structure." Observing the different layers existing above and below one another is a visually fascinating experience. Additionally, the natural texture of the unlined rock walls provides a landscape unique to this location. As you pass through the 110m stretch, you can enjoy the quiet atmosphere while observing the natural terrain. The way the tunnel integrates with the surrounding environment offers a singular sensation to all who visit.
As this spot is located along an outdoor road, you can enjoy the changing scenery of the seasons. Visiting during seasons when the surrounding greenery is lush or when the seasonal transitions are most apparent is highly recommended. During bright daylight hours, the internal structure of the tunnel is relatively easy to see, making it an excellent time for photography. However, since the interior can become dark depending on the environment, we recommend visiting during daylight hours.
Visitors can enjoy observing the tunnel as a historical structure or practicing photography. Looking up at the unique double-layered design is an experience rarely found at typical tourist destinations. It is also a perfect place to stop during a drive to check out this unique landscape in a short amount of time. You can spend a peaceful moment focusing on the intricate details of this historical structure.
Mukiyama Tunnel is located in the Southern Boso area of Chiba, specifically near Otaki. The surrounding area is dotted with nature-rich spots like the Yoro Valley and various locations to enjoy seasonal flowers. It is an ideal destination or a perfect stopover on a driving route. We recommend combining this visit with other scenic spots in the region to create a complete nature-themed travel plan.
As this is a public road and structure, there is no admission fee. No specific payment is required to pass through. Since most visitors arrive by car, it is wise to have cash or a credit card ready for gas or nearby dining.
There are no permanent information centers or staff on-site, so English signage and support are not available. We recommend understanding the structure and layout via maps before your visit.
No prior reservation is required. You are free to view or pass through at your convenience.
The area is a natural environment. We recommend wearing comfortable walking shoes. As the interior of the tunnel can be dark depending on the weather or time of day, carrying a flashlight may be useful.
Photography is permitted, but please ensure you do so safely without obstructing vehicle traffic. As this is a functional roadway, obstructing traffic is strictly prohibited.
Due to the unlined structure and roadside location, there may be uneven surfaces or steps. We recommend checking the road conditions in advance if using a wheelchair.
This is a public road. To protect the natural environment and historical structure, please follow basic etiquette, such as taking your trash home and refraining from graffiti or any acts of destruction. Since vehicles have the right of way, please prioritize safety when walking or taking photos.