Feeling a bit retarded now. I forgot that XP does that.
Prepare to feel retarded again. Forte was talking about the fact that, if you saw your map from eye level, the entrance would look like this:
V water V water
____...........____
.cliff.|..........|.cliff.
.......|_____|.......
.......|stone.|.......
It wouldn't be bad, if not for the fact that that the front was that low, but the top was higher than the cliff. so, in effect, your wall looked like this from the side:
\
.\
..\
All in all, your "wall" looks like shit