What kind of castle would you like to see for the Sylvan faction?

A huge tree on which everything (or almost everything) grows and develops – what could be better? (Now that’s what I call symbiosis with nature.) Forests, meadows, and other things have become boring. At least it’s something more or less original (although it still reminds me of the elven tree from Disciples 2). Plus, I like the unusual atmosphere; when you enter their castle, it’s unclear whether it’s day or evening there. And the music is very… tropical.