Guida
Located along Prefectural Road 300 (Ujishita-hara Line) in the mountainous region of Takahashi City, Okayama, the 'Hayama Second Tunnel' is an extraordinary structure where natural formation and man-made engineering merge. The most striking feature is that the tunnel utilizes a natural limestone cave. Standing at the northwest entrance, the towering limestone walls create an atmosphere identical to a natural cavern entrance. It is considered one of the few precious 'unlined' (raw-cut) tunnels in Okayama Prefecture, offering a rare chance to observe both historical engineering and natural geological beauty simultaneously.
The history of this tunnel dates back to the Taisho era, with construction beginning in 1919 and completion in 1921. At the time, it played a vital role in transporting goods. Historically, the 'Fukiya Route' passed through the ridge lines, transporting essential goods such as iron, copper, and red ochre (Bengala), as well as seafood from Kasaoka. To create a more efficient route along the Mikawa River, this tunnel was excavated to accommodate the increasing traffic of horse-drawn carriages and carts. Consequently, the tunnel was designed with a width of 3 meters to allow vehicles to pass safely.
There are several points of interest at the Hayama Second Tunnel. First is the northwest entrance, where the vertical limestone walls of the karst landscape create a dramatic, cave-like entrance. Second is the 'unlined' internal structure; unlike modern concrete tunnels, the interior retains its raw, natural rock surface. The tunnel is 32.0 meters long and 3.0 meters wide. Additionally, the steep limestone walls near the northwest entrance are sometimes used as a site for rock climbing enthusiasts due to their dynamic terrain.
As this is part of a public road (Prefectural Road 300), it is accessible at any time of year. Daytime is the best time to visit to appreciate the intricate textures of the limestone walls and the natural details of the karst landscape. It is highly recommended to enjoy this alongside the scenery of the nearby Hayama Valley. However, please note that the interior of the tunnel and nearby natural crevices (such as the 'Anagoya' or Seiryu Cave) lack artificial lighting, making visibility very low during the night or in dark weather conditions.
The primary way to experience this site is through scenic driving or as a photography stop. The entrance provides a perfect backdrop for capturing the beauty of natural rock formations. For outdoor enthusiasts, the surrounding cliffs are known as practice areas for rock climbing. Please note that because the tunnel is narrow, drivers should proceed with caution.
When visiting the Hayama Second Tunnel, consider combining your trip with a drive through the scenic Hayama Valley or toward the Tenryu Bridge to the west. Nearby, you can find the 'Kata-domon' (a natural rock gate where the roof seems to touch the road) and the 'Hayama First Tunnel,' which features a more modern concrete-reinforced entrance. The area is approximately 30km from the Niimi IC on the Chugoku Expressway, making it a great addition to a wider driving itinerary.
As this is a public road, no entrance fees or reservations are required. However, since it is a natural environment, comfortable walking shoes and clothing suitable for outdoor exploration are recommended. Be aware that the road surface may be damp or dark depending on the weather and time of day. Please drive carefully as the road width is limited in several sections.