Speaking of the locations, what is a significantly different location?

"Each new location must have a different visual theme and it must be obvious that you are in a new location."

My "locations" are all pretty similar, every "location" is really just a flat piece of ground with some buildings on it. The number if buildings and their looks will be different (at least a little) for all "locations" and you can do somewhat different things in each.

That way, I hope that I can fulfill the demand somewhat. I guess the "different visual theme" is a relative thing, you can't really define what "different" means more than that it clearly can't be identical.