One of my fondest memories from high school was an overnight train ride we took from somewhere in Italy to Paris during a spring break study abroad program. The majority of the rail workers had gone on strike and the only people left working the trains were the drivers. The rumors were that gypsies had taken over the trains and that they were now unsafe for normal customers. Being a large group of high schoolers in a foreign country trying to stick to a tight schedule, we didn't have much choice than to take the train or else have to deal with a logistical nightmare. When we got on, the train was deserted, and we had free reign to do whatever we wanted. That type of freedom was rare and pretty thrilling to a high school freshman.
One of my favorite New Year's Eve parties was on an Amtrack over a decade ago. I was headed back up to college and because of my schedule had to overnight it on a Northboand Amtrack on New Year's Eve. I'm not sure if it was because it was New Year's Eve, or a particularly long route, or just a special train, but it's the only time I ever remember seeing a liquor bar on an Amtrak (the entire bar was smaller than any closet in my house). I had brought my own liquor, and did my best to keep it out of sight.
Several hours before midnight, the coach I was in started morphing. Normally people didn't really talk to each other. That night, seatmates started talking, impromptu cardgames were started, I was certainly not the only one with hidden alcohol, and the bar was providing plenty for those without. By midnight the car I was in, and the adjacent car with the bar, were in full party mode. It was simultaneously one of the most surreal and awesome trips I have ever taken.
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As for the Amtrak writer program - very cool. As a young serviceman, I would frequently catch a Friday night Amtrack away from the military town I was stationed in, picking a random location that I could spend Saturday in, and then ride back Sunday afternoon. I didn't write about or photograph my travels (wish I had), but I can't image a writer worth their salt not being inspired by the scenery, events, or people met on such random jaunts.
I traveled from Beijing to Moscow on the trans-Siberian train. It took five days.
One tip: if you're thinking of making the journey, bring a small hose with you so you can hook it onto the sink and have a little shower. Also, there are companies that will arrange home stays if you want to get off in Yekaterinburg or a few other towns and kick around for a bit.
In the early 90s, I traveled from St Petersburg, Russia to London's Victoria Station. I'm pretty sure the route does not exist any more, as it involved going through all the Baltics, Poland, Berlin, and eventually the Oostende-Dover ferry and on to London. All in all, it took about three days (including a 12-hour layover in Berlin).
Also, this guy documented his trip from Vienna to Pyongyang, North Korea: http://vienna-pyongyang.blogspot.com/