The Auschwitz sign with its inverted "B"
For people the world over, few relics have come to symbolise the Nazi Holocaust more than the infamous wrought-iron sign straddling the entrance to the Auschwitz death camp, bearing the cynical words Arbeit Macht Frei.
The gate itself was constructed under German orders by Polish political prisoners who had arrived in late 1940 and early 1941.
Its construction was part of a general overhaul of the camp, which included replacing temporary barbed wire with high-voltage fencing and concrete posts.
The 5m (16ft) sign was made by prisoners in the metalworking detail under Jan Liwacz, a master blacksmith.
It is believed that, in an act of defiance which went unnoticed, the prisoners reversed the B in Arbeit, giving it the appearance of being upside down.
Locals also say that after the camp was liberated by the Soviets in 1945, Red Army soldiers took down the sign and were preparing to transport it back to the Soviet Union, but were bribed by local Poles to leave it.
The phrase Arbeit Macht Frei itself was coined by the 19th Century linguist, ethnologist and author Lorenz Diefenbach.
The Weimar Republic in the 1920s, and later the Nazis, were both attracted to the leading character of Diefenbach's book Arbeit Macht Frei, whose achievements are defined by concentrating on doing his work.
Pope Benedict insisted on walking alone under the sign
Weimar politicians used the phrase to promote employment policies.
Then the Nazis latched on to it and a sign bearing the inscription appeared at the Dachau concentration camp, set up by Heinrich Himmler in 1933 to use dissidents as slave labour.
The phrase later became part of the Nazis' deception for the real use of the concentrations camps.
Ultimately for most the freedom referred to could only be achieved in death.
Jan Liwacz did survive the war. He was released from another concentration camp in May 1945 and returned to Poland.
His sign is occasionally removed by officials for conservation work and a replica is used as a substitute - the replica is now being used again to replace the stolen original.
Several months of conservation were done in early 2006 ahead of and after a visit by Pope Benedict XVI in May of that year.
The surface had deteriorated and was treated with extra preservation materials. The replica was made in the workshops of the Auschwitz-Birkenau Museum.
Pope Benedict insisted on beginning his emotional visit by walking alone under the infamous sign and saying a prayer in front of the reconstruction of the execution wall where Nazis lined up and shot thousands of prisoners.