A Russian historian claims he's close to solving one of the biggest unsolved mysteries from World War II. Sergey Trifonov, a historian from Kaliningrad, has put forward a new theory concerning the famous Amber Room whereabouts. 

Sometimes dubbed the Eighth Wonder of the World, the Amber Room disappeared in the chaos of World War Two and all attempts to trace it have so far failed.
 
Nazi troops brought the room to Koenigsberg, now Kaliningrad, but it's not known where they hid it.
 
However, Sergey Trifonov believes the Germans concealed it right in the centre of the city – in one of the tunnels under the Pregolya river – before leaving Kaliningrad in April 1945.
 
Moreover, he thinks it is not only the Amber Room but many other treasures that are hidden underwater.
 
If his theory is right, it seems the Germans chose a storage site particularly suited for amber.
 
The constant temperature under the river is around 2 degrees  – optimal conditions for amber which, if kept elsewhere, would have been destroyed by temperature fluctuations.
 
A recent diving expeditition failed to find the tunnel, partly because of low visibility.
 
“We'll need a lot of people for this work but even so it could take us quite a while before we find the entrance to the tunnel,” Mr Trifonov said.
 
The historian's theory has attracted Russian and German experts. The latter are planning to come to Kaliningrad next spring to help search for the Amber Room.
 
The original Amber Room was created at the beginning of the 18th century in Prussia and was later presented to Tsar Peter the Great.
 
While the original Amber Room is still a mistery, the creation of its beautiful copy has come true. In 1979 a reconstruction effort was made in Russia based on old black-and-white photographs.
 
The reconstructed Amber Room was almost complete in 2003 when it was inaugurated in the Catherine Palace in Saint-Petersburg – its home before it was driven to Kaliningrad.