IT WAS the most opulent of Tsar Peter the Great's rooms, brought to his new capital of St Petersburg on 18 horse-drawn wagons in 1716, a present from the King of Prussia.
The fabulous Amber Room contained six tonnes of the precious resin and took 10 years for some of Europe's top craftsmen to complete.
But more than 60 years ago it was plundered by Nazis as they stormed across Europe, never to be seen again.
Now, after years of searching, a team of treasure hunters believe it is at the bottom of an Austrian lake.
A group of American divers will today begin a 7 million project searching the 338ft-deep Lake Toplitz situated in the heart of Austria.
Norman Scott, the founder of Global Explorations, and his team plan to use small machines and unmanned submarines, which will allow explorers to spend more time underwater, as well as limit any potential harm to the lake.
Scott says the team was initially looking for Nazi gold but discovered evidence that the Amber Room was in the lake. He has a local witness - whom he will not name - who he says specifically counted 27 crates going to the waters of the lake in April 1945, one month before the capitulation of Nazi Germany.
Paperwork from the RHSA - the Reich Main Security Office of the SS in wartime - shows that the Amber Room was packed into precisely 27 crates before it was taken away by the Germans. The team also say the Cyrillic lettering on the remains of a wooden crate, bearing the words 'fragile' and numbered could mean it once contained a piece of the Amber Room jigsaw.
Scott said: "The Amber Room went somewhere and our research shows railway links with Knigsberg [now the Russian city of Kaliningrad], where it definitely was, meant it could have been transported here within three to four days, even allowing for allied bombing disrupting communications."
Under Austrian law, the profit from recovered materials will be divided between the Austrian government and Global Explorations, with a portion going to the Jewish Federation. If ownership can be determined, the Austrian government forfeits profit to the heirs, who will then negotiate fees solely with Global Explorations.
Lake Toplitz was used by Hitler's forces in the last two years of the war for secret underwater experiments using dynamite and rockets, but it later turned it into a dumping ground for anything the Nazis wanted to hide from the advancing Allies.
Until now, the lake has yielded little, except forged five pound notes - printed by the Nazis and intended to cause chaos for the British economy.
The Amber Room was an opulent baroque masterpiece presented by Frederick William I, the "Soldier King" of Prussia, to Peter the Great in 1716 as part of a move to cement a military alliance against the Swedes.
The 16-foot jigsaw-puzzle style panels were constructed of more than 100,000 perfectly fitted pieces of amber, first situated in the Tsar's Winter Palace in St Petersburg. In 1755 it was moved to the Summer Palace at Tsarkoe Selo, 17 miles south of the Imperial Russian capital.
In 1941, the approaching Nazi army surrounded the city, then known by its Soviet name of Leningrad. Tsarkoe Selo was one of the outlying areas occupied by the Germans. They packed the amber panels in 27 crates and shipped them to Germany, where they vanished.
Some believed they were melted down by the Germans, others that they were destroyed during the ferocious Red Army attack on the East Prussian city of Knigsberg where they were stored. Another theory is they were shipped out on a Nazi ship which was torpedoed in the Baltic by the Russians. In 2003 a TV documentary in Germany suggested the room, worth 120m at today's prices, lay abandoned in mine workings in the former East Germany. This was never proved.
The treasure hunters hope the Germans moved the Amber Room to Austria and dumped it in the lake to hide the evidence of Nazi looting.
A spokesman for the US treasure hunters said: "All we have done is to put two and two together to come up with a pretty convincing argument for what we believe lies down there. It was not for nothing that the area was declared a top security zone by the Nazis during the Second World War."
Diving in the lake is strictly prohibited without special permission from the authorities. The few official dives have unearthed little more than war relics, including the counterfeit UK currency, as well as false stamps, dynamite, weapons and other memorabilia. A hitherto unknown worm that survives without oxygen was also discovered by a scientific team.
Authorities admit there is no way of telling how many "unofficial" dives for treasure have been made in the lake.
Some have paid with their lives in the search for Nazi bounty in Toplitz. Alfred Egner, 19, was the first to die when he was hired by a pair of former SS officers to dive into the lake in 1963 to search for watertight tubes they believed contained the numbers to Nazi Swiss bank accounts full with the loot from conquered lands.
In 1979 a reconstruction effort began at Tsarkoe Selo, based largely on black and white photographs of the original Amber Room before the Nazis dismantled it.
The work was completed in 2003 and the restored room was opened by Russian President Vladimir Putin and German Chancellor Gerhard Schrder at the 300-year anniversary of St Petersburg.