It was described as "the Mona Lisa" of Vienna and for years was the main attraction of Austria's Vienna Belvedere Gallery: Gustav Klimt's 1907 portrait of Adele Bloch-Bauer I, known as The Lady in Gold, is one of the most famous paintings in the world.
The story of how it came to be moved from Austria, to hang in the Neue Galerie in New York, is now the story of a film, Woman in Gold, starring Dame Helen Mirren.
"It was theft by the Nazis," says Dame Helen.
"That painting belonged to the family of an Austrian Jew called Maria Altman, of which she was the surviving member after the Holocaust. Adele Bloch-Bauer was her aunt.
"The Nazis looted the painting and after the war it took pride of place in the Belvedere. Maria mistakenly believed for years it had been donated to them, and it was only at the age of 82 after discovering the truth, that she launched a lawsuit to get it back."
Made by BBC Films and directed by Simon Curtis, who made My Week With Marilyn, Woman in Gold sees Dame Helen [clearly playing Maria a lot younger than she was] starring opposite Ryan Reynolds, who plays the young lawyer who took on Altman's case.
The Austrian government refused to settle with Altman because, the actress says, "the problem was that they were iconic pictures. At the time of painting by Klimt, they were thought of as being decadent, and even though they were looted, the Nazis didn't particularly approve of them".
"But after the war they ended up in the Belvedere, the British equivalent of the National Gallery, and when you went to Vienna, if you bought a souvenir mug or fridge magnet, it would probably have The Lady in Gold on it. Then there's this little old woman saying: 'I'm sorry, that's mine'. The shock was huge.