Biggest? Not after last year.
An amber mosaic from the Amber Room was located and returned to St. Pete a few years ago. Some Wehrmacht guy had waited 50 years to try to sell it; he advertised it and the authorities pounced on it. He had apparently found it in East Prussia during the German retreat in 1945, knew what it was and decided it was finally safe to sell it. No one has any idea where the rest of the Amber Room went.