I’ll see you one tunnel, and raise you one underwater dome city!tunnel to Europe. Then you can simulate the speed by flashing lights past the windows once in a while but otherwise keep the windows closed as nothing to see.
Get some stick footage of England and france and if you realky want to send a few actors to record a few scenes that you intermix in the show.
With Sci Fi, go big in concept. Keep the actual sets brief, cheap, and evocative. Viewers want to buy into the fantasy and will do so, unless we do something stupid which yanks them out of it.
And I like the idea that if we really need a Paris street scene or an icon, we can maybe get by with two actors instead of the whole bunch! 😃