This particular background took a very long time to get right. Athough, that being said I'm still not entirely happy with it. Working upwards, you can see the different layers that are in this layout. There needs to be a foreground and a backround because the 3D train needs to be composited in between the two, to make it look as if it's really in the shot.

The foreground, after many minor tweeks was ready fairly quickly however the very back of the shot was tricky. I wanted the right angle to show the steepness of the hill, yet keep the cathedral at the very top. Also I wanted it to be off centre and skew slightly. That's the bit I'm not too excited about.

If the hill was skewed too much the buildings looked out of proportion, or it didn't look steep enough, eventually I settled with the one 2nd from the top. And after a suggestion to make a more faded look to the background from Sean, I came up with the layout that will be used in the final film.