I travelled a lot when I was young… then I got married, had kids and worked as a teacher for 15 years. I went back to university to do a Masters in my 40s and worked for another 15 years in a university psychology department as a placement tutor. I took early retirement, worked one season for EF with American high school students then saw an advert for a Great Rail Journeys Glacier Express holiday in a magazine. I contacted the company who just happened to be recruiting at that time.
So hard to choose - but it's probably the Bernina Express… if the sun is shining!
The Arctic Circle in mid-summer; there's something truly special about being somewhere that has 24 hours of daylight.
Take every opportunity to talk to the locals - on trains, in restaurants, in the street and if you can manage even a few words of the local language they will be impressed and delighted.