Khun Tan Tunnel

Khun Tan Tunnel runs about 1,352 metres through the mountain pass between Lamphun and Lampang, and it’s Thailand’s longest railway tunnel — cut through solid rock on the Northern Line between 1907 and 1918. It’s still a working section of track, so the way to experience it is by train or from the platform at Khun Tan station, not on foot inside the bore.

Khun Tan station sits roughly 200 metres from the tunnel’s northern portal, at 578 metres elevation — the highest railway station in Thailand. Regular Northern Line services between Chiang Mai and Lampang (continuing on to Bangkok) pass through several times a day; ride one through the tunnel and you get a few minutes of total dark, a noticeable temperature drop, and the sound of wheels echoing off stone before daylight reappears at the far end. Watching from the station platform as a train enters or exits the mountain is the other way to see it, and it’s the one that doesn’t put you anywhere near live track.

Watch out: This is an active mainline tunnel, not a walking trail — trains pass through on a working schedule, the bore has no lighting or walkway for pedestrians, and there’s no safe refuge space inside if a train comes through. Stay on the station platform or the marked park trails.

The station and tunnel sit right at the edge of Doi Khun Tan National Park, whose entrance trails start close enough to the tracks that most visitors combine the two: view or ride through the tunnel, then walk into the park for the forest trails and the cooler mountain air the pass is known for. The surrounding terrain is thick with the mist and teak forest typical of this stretch of the Chiang Mai–Lampang range, and the roads up to the station are narrow and unpaved in places, so this isn’t a drive-up stop — arriving by train is the practical route.

Insider Tip: Take a day train rather than the overnight service if the tunnel and the mountain scenery either side of it are the point of the trip — the sleeper trains often cross this stretch after dark.

Bring a light jacket for the temperature drop inside the tunnel and layers for the cooler mountain air at the station generally. Comfortable walking shoes are worth it if you’re continuing into Doi Khun Tan National Park afterwards — the trailside terrain is uneven in places, and the station approach road is narrow and sandy underfoot.