A Polish historian on Friday claimed he had found the Amber Room, a long-lost Russian treasure looted by the Nazis during the Second World War.
Bartlomiej Plebanczyk said he believed he had located the missing artwork in a German wartime bunker in north-eastern Poland.
Radar tests showed there was a secret chamber at the back of the bunker where the treasure could be hidden, he said.
The claim comes after two treasure-hunters said they had discovered a Nazi gold train hidden in Poland last year — only for an extensive search to find no trace of it.
The Amber Room was an 18th century chamber decorated entirely with panels of amber and gold that was regarded as an “eighth wonder of the world”.
It was seized by Nazi troops during the war and taken to the then German city of Königsberg, in what is today the Russian enclave of Kaliningrad.
It disappeared after the war. An official Soviet investigation found that it was almost certainly destroyed either in RAF bombing or by Russian shelling.
But rumours that it somehow survived have persisted and it has long been sought by treasure-hunters.
Mr Plebanczyk says he is “almost certain” he has found it.