My first train journey outside England was in 1963 on a school holiday to Germany & Austria. The route was from Victoria to Dover Marine, then a BR ferry to Ostend, arriving at about 05:30. We were allowed onto our train waiting in the station. As young'ish teenagers we were probably not as orderly as the treachers might want so we went exploring. The trains were completely different to what we had been used to, (much bigger, pull-down seats in the corridor, half opening windows and inward opening doors). At on point a railway employee asked us (in flemish I presumed which none of us understood). After a shrug on shoulders, he asked: "take me to your leader" which of course we found quite amusing.
That first train took us all the way to Koblenz, via Bruges, Ghent, Brussels, Liege, Where the SNCB electric loco was replaced by a steam loco. I have no idea what sort as we were at the rear of a long train but we could see, hear and smell it as it climbed over the hills along a very twisted route via Verviers. From Aachen onwards, a German electric loco made for a smooth and uneventful journey southwards although I do remeber the view from the train of Cologne city centre including the cathedral.
Overall I would love to have been aware more of the railway aspects of the holiday. From a short break in Koblenz, we went by train down the west bank of the Rhine Gorge to Heidelberg. A few days later from Heidelberg to Salzburg with a 3 hour break in Munich. Then a week later, by OBB train from Salzburg via Linz to Vienna. The whole journey back was overnight on a couchette to Ostend taking about 15 hours. The initial journey to Koblenz was the most interesting though.