In 2006, Renfe introduced a new type of rolling stock for Alvia trains that was able to switch from Iberian to International gauge without having to stop and maneuver the train.(1)
It's 2026 and I am in an Alvia train that has now been stopped for several minutes at the gauge switching tunnel(2), lights off and everything.
(1) I just learned this from Wikipedia, I am not a train nerd!
(2) Hence I have no clue how the "gauge switching tunnel" is actually called 😅