@mengel It's about 1500 EUR of train tickets (traveling first class only, in 2nd or 3rd class it's waaaay less). I'm spending a day in Kunming to look at the city because a friend recommended me to do so, apart from that a day in Beijing, three days in Ulaanbaatar (due to the train schedules, my connecting train to Siberia only runs once every second week) and a full day in Saint Petersburg (also due to the train schedules).

How to plan that ... Hmmm, that's a good one. I guess with some decent knowledge of worldwide railways it's more or less feasible. I planned four different routes where one is currently not possible due to Iranian civil war, the other one is not possible since my visa was denied and the third one is partially by ship which is cheating. So the proposed itinerary it is. Idk, when you have a rough understanding of the railway connections leaving Europe, the Silk road and the Russia-China railway borders, then it's actually pretty straight forward to plan.