The tunnels were part of the 'Old Chuo Line' that connected Nagoya to Nagano through the mountainous Kiso Valley.
The tunnels were constructed using a distinct 'English bond' bricklaying method common in early 20th-century Japanese infrastructure.
The tunnels were sealed for 40 years before a citizen-led group cleared the overgrown mountain paths to reopen them in 2005.
Several tunnels in the series were intentionally filled or collapsed to prevent entry before the preservation project began.
The tunnel walls still show distinct soot stains from the steam locomotives that powered trains through the pass for over six decades.
The Aigi Tunnel is a series of red-brick railway tunnels constructed in 1900 as part of the old Japanese National Railways Chuo Main Line. Following the line's relocation in 1966, the tunnels were abandoned until local preservation groups rediscovered and restored them in 2005. The site features multiple tunnels and bridge piers built with masonry and brick techniques characteristic of the Meiji period. It serves as a living museum for railway heritage, allowing visitors to walk along the original ballast and path through the dark, arched corridors. The site is located within the lush valley of the Shonai River, surrounded by forested hills. Preservation efforts are managed by the Aigi Tunnel Preservation Society, which maintains the trail for public access during limited seasonal openings. The area retains historical artifacts including mileposts and rail-related stone markers.
The entrance to Tunnel Number 3, where the contrast between the green forest and the red brick archway is most prominent.
Wear sturdy, closed-toe walking shoes as the path consists of uneven railway ballast and gravel.
Bring a flashlight or headlamp as the tunnel interiors are unlit and become very dark toward the center.
Check the official website before traveling to confirm the specific dates the tunnels are open to the public.
Attempting to visit on weekdays or outside of the designated open-house weekends, as the gates are locked to protect the structure.
Open only on specific weekends during spring and autumn; closed on weekdays and throughout the summer and winter months.
Stay on the designated gravel paths, refrain from touching the historic brick walls, and carry out all trash.
