Memory is a little hazy now, but in the area of Spandauforst, in the NW corner of the British sector, the Wall was set back inside DDR territory by at least two hundred yards in places. I believe there was some evidence that these tracts of open ground, much of it heath, may have been used by the Sovs/HVA/MfS for brief nocturnal(?) meets with sources resident in West Berlin who, for whatever reason, were not required to cross into the Russian sector, possibly because they might have run the risk of attracting unwelcome Western attention by doing so. (One can but speculate as to who they might have been - and not necessarily Germans!) I remember the curious find, around 1980, of a small two-man hide containing a solitary microphone, well concealed in dead ground about halfway between the Wall and the edge of the wood, but definitely inside the DDR. Interesting times.