A stolen masterpiece by the Austrian symbolist Gustav Klimt has been recovered and authenticated. <em>Portrait of a Lady, </em>painted around 1916, went missing 23 years ago from a gallery in Piacenza, Italy. A gardener found the $66 million (Dh242 million) painting in December, inside the walls of the very same building it was stolen from. The painting shows a woman with blue eyes and rouged cheeks standing in front of a green backdrop of wild brushstrokes. It was at the centre of one of Italy's highest-profile cases of art theft when it disappeared in 1997. <em>Portrait of a Lady </em>was part of a series of women's portraits that the Austrian artist painted between 1916 and 1918. It<em> </em>was painted on top of another older portrait by Klimt. It is the only known double Klimt in the art world, something that adds to the painting's value and helps in the authentication process. The first portrait was supposedly of Klimt's former partner who had died and was painted over out of grief. The gardener who found the painting said he was clearing out ivy from around the property when he uncovered a hole in the wall. Inside was a trash bag with Klimt’s masterpiece. “I found this box inside a black sack and at first I thought it was trash, but then I called my superiors right away,” he told Italian media. Investigators have now verified the painting’s authenticity but will hold on to the work to uncover clues about who stole it. When the painting vanished 23 years ago, police said they believed thieves had used a fishing line to hook it off the wall and haul it up through an open skylight to the gallery roof where the frame was discarded. Authorities are now investigating to find out if the painting had been stashed in the gallery’s walls with the intention of retrieving it once the worldwide media hype surrounding the robbery had died down. The theft had mystified the art world for decades. It sparked conspiracy theories and rumours that gallery staff aided the act and that the painting had fallen into the hands of a satanic sect. The case was closed not long after the robbery due to a lack of evidence. It was reopened in 2014 after police hoped that advances in DNA technology would help them identify a partial fingerprint left on the painting's frame. Nothing came of it. In November 2015, a man came forward claiming to be the painting's thief and demanding a ransom for it. But that led nowhere as well. The Mayor of Piacenza Patrizia Barbieri and the head of culture, Jonathan Papamarenghi, hailed the "historic" news and vowed to make the 1916 portrait a centrepiece of the city's heritage. "After the joy of the find ... the conflicting rumours of these days have fuelled even more suspense over a story that has mysterious aspects," the two local officials wrote. When the workers found the painting, Mr Papamarenghi said he was impressed by its excellent condition after decades lying in a wall. He said it was second on the list of the most valuable artworks missing in Italy, behind a work by Caravaggio stolen from a church in Sicily in 1969. Klimt is most famous for <em>The Kiss, </em>an oil painting with added gold leaf, silver and platinum. He was one of the leading Symbolist painters of the early 20th century and was an important influence on his contemporaries, including the Austrian painter Egon Schiele. Love and intimacy are common themes across Klimt's work, and his primary subject was the female figure.