Tsk...My house is 300 years old, and there's even a clause written into the deed that I have to maintain historical accuracy as much as possible on the exterior (even landmarks and National Registry homes don't care about anything other than the exterior). I've got a swimming pool, not a pond, I suppose that is different. MetLife insured it for exact replacement for about $1300/year; my house is considerably smaller than yours, though (only 2500 sq. ft.). I've got oak paneling in my house that's so wide, if you wanted to find an exact replacement you'd have to go to a national park with old-growth forest. 
Try MetLife. They insured my house well enough that Norm Abrams would re-build it using hand tools if it ever was damaged.