How Japan Built the World's Deepest Tunnel Where No Machine Could Work

240 metres below the sea, the Seikan Tunnel took Japan 21 years to build. Engineers abandoned boring machines for hand-drilled tunneling through volcanic rock. A 1954 ferry disaster killed 1,430 people, forcing the decision to go under the strait. It's still the deepest railway tunnel on Earth. #engineering #civilengineering #megaprojects #documentary #japan #tunnel #megaprojects #howitsbuilt ⚠️ IMPORTANT: ABOUT THIS VIDEO ------------------------------------------------------------------- This is an educational documentary analyzing the engineering and construction of public infrastructure, based entirely on open-source information. All visuals and animations are 100% synthetic, AI-generated conceptual representations. No real footage of the construction sites or personnel was used. This video is purely informational and intended for educational purposes only.