This screeny shows an important feature of the area where I live.    Without 150 metre mesh terrain the small mountain area is totally flat but fortunately it is now a reasonable copy of the real thing.

All the area outside the line I have drawn does not exist, nor do the buildings on it.     Basically a walking track around the Mountain's base falls into the water.

My query is, can this area be removed.   I have seen many add-ons done over existing terrain but wonder whether Microsofts non-existent land  can be removed as well ?