Sadly I cannot really use Visitor properly with my system, so I tend to stick to WrpEdit.
So, I am not at all familiar with the ins and outs of Visitor.
Maybe the forest square Visitor wants is in fact a forest square.
There is one, but if my memory serves me correctly it is a solid piece and cannot be entered.
I have a vague notion that there is one other square piece that can be entered, but it has been a long time since I talked to the trees.
Planck