6.8 x 6.8 x 6.8 studs
This is a variation
of an idea for a 6.8
stud diameter sphere with a 4x4x4 "core." After rebuilding
it for BricksWest 2003, I decided to convert it to grey, take out
a corner of it and put a dark grey 2x2 radar dish in there. For
the trench I used pieces that'd make a complete line around the
middle of it (e.g. using two 1x2 plates instead of a 2x2 plate).
I think it turned out alright. I plan on making a Death Star II
in the future.