Tho carrara 4 especially has good terrain and sky. If you try some complexity with trees you will be rendering forever. I feel that other outdoor objects would be more of a challenge in c4. With plugins you can do more, but it is more all around or complete than bryce or vue unless you go vue 5 I, which is a whole other ball park even still for modeling you would probably need something else. Bryce and Vue limit file support. All the commercial companies tend to do this which can be very annoying.

No need to think outside the box....
    Just make it invisible.