It’s cold, it’s very, very noisy, and—if I can be quite honest with you—I’m not feeling super relaxed. I’m currently around 300 meters, or 1,000 feet, beneath the North Sea, in a dark, dank cave. It smells weird.
Source: [MIT Tech Review](https://www.technologyreview.com/2026/06/22/1138821/inside-worlds-deepest-longest-subsea-road-tunnel/)