The new Stadttunnel bike tunnel running under the main train station in Zurich.
So cool. I found an article about it here:
https://www.motion-mag.com/articles/zurichs-stadttunnel-reinvents-urban-infrastructure

It’s not every day that a relic from a shelved 1960s highway project becomes the hero of urban cycling. But in Zurich - where city planning often dances between tradition and innovation - that’s exactly what happened. Welcome to the Stadttunnel, a once-forgotten stretch of concrete beneath Zurich’s main station that has been reawakened as a state-of-the-art cycling tunnel. With its grand reopening in May 2025, it now connects District 4 and District 5 quickly, safely, and stylishly - all without needing to brave the chaotic city traffic above.