When I was interrailing I'd try and do some across Europe night trains as it meant I saved on hostel costs and I'd wake up somewhere new. The choices are somewhat limited though
We did that a lot as well. Night trains are the closest mankind has to teleportation. Hop on a train in Berlin, have a beer, sleep, wake up in the centre Paris or Rome with a coffee and a croissant.
The closest we have to teleportation is airplanes (i.e. shortest travel time). Sleeper trains are more like cryostasis ships. The journey takes forever, but you don't notice.