[RightWhale]

We have seen the marbles. We are done with them, there is nothing more to be learned. They can safely be returned as a gift to the site where they can rot.

[Dog Gone]

Had the Greeks kept them, they would have been forever destroyed as were most of the marbles that were left behind in Athens to disintegrate in the heavy air pollution which blankets that city.

The Greeks are building a musuem at the Acropolis which presumably has air filters and returning the marbles now would not endanger them. But I don't know that for a certainty. Ideally, they would have been preserved and protected while they were part of the Parthenon. They weren't, and it's doubtful they'll ever be placed back on that structure.