Give me a shout when you pass Rotterdam i'm gladly giving you a tour!
Okay Netherlands is nice, but before trains I recommend you to check ships if you'd like to sail the Balt sea, because you could do like Estonia, Sweeden, Finland and Denmark - then back to Estonia.
It probably depends on what you're looking for but these countries offeres you good access to both the nature and amazing historical capitals.
I never experienced that but Im already envy, just not sure about ships availability and speed, so you won't spend most the time sailing :)
edit: I just realized you probably getting to Europe by Ferry or sth lol
Whole the idea is great, I have pretty much explored the scandinavian area to its' fullest already :P Lived in Finland for over 12 years, hiked around Sweden and Norway a lot haha😁
I have adjusted my plans to add an extra day for The Netherlands alone :)