Qualla: Daishimizu Tunnel

Daishimizu Tunnel: Introduction

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit T.Kambayashi, CC BY-SA 3.0. Somewhere beneath the mountains on the border of Gunma and Niigata Prefectures, a bullet train is hurtling through 22.2 kilometers of darkness at 240 kilometers per hour. The passengers barely notice. They are reading, sleeping, scrolling through phones. The tunnel takes about six minutes to cross. It took construction crews more than a decade to build, cost the lives of 16 workers, and for a brief period held the title of the longest railway tunnel on Earth. The Daishimizu Tunnel is one of those engineering marvels that succeeds so completely it becomes invisible -- a problem solved so thoroughly that no one thinks about the problem anymore.

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Image: T.Kambayashi | CC BY-SA 3.0

Daishimizu Tunnel: The Mountain Barrier

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit Tam0031, CC BY-SA 3.0. Japan's central mountain range runs like a spine down the length of Honshu, dividing the country into two fundamentally different worlds. To the east lies the Kanto Plain, home to Tokyo and the dense urban corridor of the Pacific coast. To the west lies the Niigata region, facing...

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Image: Tam0031 | CC BY-SA 3.0

Daishimizu Tunnel: Sixteen Lives Underground

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit RSSFSO, CC BY-SA 4.0. Construction of the tunnel was an ordeal. Workers bored into rock deep beneath the mountain ridgeline, contending with extreme water pressure, unstable geology, and temperatures that climbed as they pushed deeper. The tunnel was completed in 1978 after years of grueling excavatio...

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Image: RSSFSO | CC BY-SA 4.0

Daishimizu Tunnel: The World's Longest -- Briefly

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit RSSFSO, CC BY-SA 4.0. At 22.2 kilometers, the Daishimizu Tunnel held the title of the world's longest railway tunnel upon completion. It was a record Japan would not hold for long. The Seikan Tunnel, connecting Honshu to Hokkaido beneath the Tsugaru Strait, surpassed it when it opened in 1988 at 53.85...

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Image: RSSFSO | CC BY-SA 4.0

Daishimizu Tunnel: Water from the Mountain's Heart

Mon, 16 Feb 2026 00:00:00 GMT

Photo credit 切干大根, CC BY-SA 4.0. During construction, drilling crews struck something unexpected: veins of pure, naturally filtered spring water flowing through the rock deep inside the mountain. Rather than treat this as an engineering nuisance to be pumped out and discarded, someone recognized an opportunity. ...

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Image: 切干大根 | CC BY-SA 4.0