A painting that was discovered hidden inside the walls of an Italian art gallery last month, has been confirmed to be Gustav Klimt's 'Portrait of a Lady', according to art experts. It had disappeared from the gallery during renovations in February 1997. The discovery of its authenticity has helped solve one of art world's biggest mysteries but raised certain questions like who took the painting. A gardener at the gallery was clearing ivy from the gallery's walls, when he found a bag with the painting last month. Using infrared technology and radiation, the painting was determined to be the original one.