MMO Game World

What is the best free tool to make game worlds?
If any of you have played WoW then you’ll know the sort of world that I am talking about, only smaller.

Needs to be Unity compatible without having to buy stuff.
I have tried Bryce 7.1, but there’s no good tutorials for it and it feels a bit clunky.

Any ideas?

I’ve just found that blender can do it, is this the best option?

it is the best option for free.

OK, ty

I have had a go with it and it’s quite easy actually, I’ll stick with it.