Link to the interactive map: https://back-on-track.eu/night-train-map/
Night trains are amazing. It's basically a mobile hotel room that's a little cramped, but spits you out in another country at 7:00am.
You may be woken by someone yelling something in Romanian at 2:00am when the train stops. And you may be woken for passport control at 3:00am, so try not to be naked when that happens. (Lessons learned)
Some snacks, a bottle of wine, and a good time. Night train!