@borkdude I've traveled many times from Holland to Finland on trains and busses. One comfortable is was Adam-> Rostock 🛳️ -> Helsinki (24 hours on the ferry which is quite relaxing, and at least did not used to be super expensive if you do not have a car). Fastest i guess, was Adam -> Hamburg -> Copenhagen -> Stockholm ⛴️ -> Helsinki. But ferries are apparently not any more environmentally friendly than flying. Also done Adam -> Berlin -> Warshaw -> Riga -> Tallin -> Helsinki (short ferry at the end). Very nice, but, alas takes more time. So it depends on how much of a hurry one is in. All of those are nice, though