London to Athens...

[BEP]

So I am flying into London on July 20th with friends... We need to make it to Athens by July 25th. We don't want to fly, just take the trains.

I'm pretty sure that Munich is going to be the first stop. After that I really am not sure. Ljubjana, Slovenia, and Croatia look like the next logical stops after that.

What is it like traveling through the former Yugoslavia? Any great cities to check out/avoid?

Are there other routes I should consider in this quick trek across the continent? We will have much more time to travel after our stay in Greece.