You told me you cant shatter diamond, but could you make a window out of it? Diamond is not indistructable, so I imagine if you were to make a window out of it it would be pretty thin and apt to breakage.
The only way you can get through diamond is w/ dynamite (or other exsplosive) or a diamond cutting drill bit. And yes if you had a window made out of it it would be virtually indestructable.