The discovery of a secret Second World War tunnel network has raised hopes of finally finding the lost Amber Room treasure looted from the Soviet Union by the Nazis.
Five entrances have been discovered in a 200-hectare forest in north-east Poland, near the Russian exclave of Kaliningrad. The site at Mamerki was already well-known for the bunker headquarters of the German army's Supreme Command of the Land Forces.
"At the moment, based on how the entrances are spaced out, it looks like one of the tunnels is about 50 metres long, but it could be longer," Bartlomiej Plebanczyk of the Marmeki bunker complex museum told the MailOnline. "Some of them have been filled in, perhaps in order to hide them, so we will have to remove a lot of material before we can see what is inside them."
The Amber Room, decorated with intricately-carved amber panels, was looted by Nazi troops from the Catherine Palace 20 miles south of St Petersburg — then Leningrad — in 1941 early on in the German invasion of the USSR.
Soviet curators at the palace pasted wallpaper over the room to disguise it after attempts to remove the panels found they had become brittle over time. But the work of art was too famous for the deception to succeed, and the room was transported to Königsberg castle in East Prussia — now Kaliningrad.
During the final collapse of the Wehrmacht in January 1945, German Führer Adolf Hitler issued an order prioritising the transport of looted artefacts from the city to Germany. However, Nazi Gauleiter of East Prussia Erich Koch abandoned his post before the order could be carried out.
"The tunnel is part of a hitherto unknown system of underground corridors that requires careful penetration," Plebanczyk said. "It may be an ideal place to hide treasure. Will it lead to the Amber Chamber? So far nothing can be ruled out."
The Amber Room was originally constructed in Berlin from 1701 onwards for the first Prussian king Frederick I. Frederick gifted the treasure, known as the "eighth wonder of the world" at the time, to his ally Russian Tsar Peter the Great in 1716. Peter had it transported to the Catherine Palace and reconstructed over a period of ten years. It was later expanded from its original form, containing 450 kg of amber, to six tonnes of the semi-precious substance.
The modern-day value of the lost treasure has been estimated at up to $500 million. A reconstruction of the room at the Catherine Palace — which the Nazis vindictively destroyed as they were forced to retreat in 1944 during the Red Army's Operation Bagration — was begun by Soviet authorities in 1979, taking 24 years to complete.