i have to imagine they'll salvage any stone they can and build up around it as others have mentioned. we were in venice a few years ago, and there's a famous opera house that caught on fire, burned down, and apparently took a large part of the neighborhood with it. it was being worked on by contractors at the time. as the story goes, in italy, (not sure if this applies to europe or how this works) if a contractor is not on schedule, they'll be penalized for being late. apparently to avoid this from happening, one of the workers set a small fire to back up the schedule and avoid that penalty. well...it raged out of control, and did more damage than anyone could have realized. they'll rebuild, but i can't imagine how much history is lost there.