Art experts have confirmed that have determined that a stolen painting discovered hidden inside an Italian art gallery's walls is Gustav Klimt's "Portrait of a Lady."

A gardener at the Ricci Oddi Modern Art Gallery in the northern city of Piacenza reported finding an art work last month while clearing ivy. “Portrait of a Lady” was stolen from the gallery nearly 23 years ago.

"It's with no small emotion that I can tell you the work is authentic," Piacenza Prosecutor Ornella Chicca told reporters Friday.

This image taken from a video distributed Wednesday, Dec. 11, 2019 by Italian police shows two police officers standing next to painting which was found inside a gallery's walls, in Piacenza, northern Italy. A gardener at the Ricci Oddi modern art gallery in the northern city of Piacenza told Italian state TV on Tuesday that he was clearing ivy from the gallery's walls when he noticed a metal panel in which he found a bag inside a space within the walls. When the bag was opened it contained a painting that might be Klimt's “Portrait of a Lady,” which disappeared from the gallery during renovations in February 1997. (Italian Police via AP)

This image taken from a video distributed Wednesday, Dec. 11, 2019 by Italian police shows two police officers standing next to painting which was found inside a gallery's walls, in Piacenza, northern Italy. A gardener at the Ricci Oddi modern art gallery in the northern city of Piacenza told Italian state TV on Tuesday that he was clearing ivy from the gallery's walls when he noticed a metal panel in which he found a bag inside a space within the walls. When the bag was opened it contained a painting that might be Klimt's “Portrait of a Lady,” which disappeared from the gallery during renovations in February 1997. (Italian Police via AP)

The portrait, of a young woman sensually glancing over her shoulder against a dreamy green background, was displayed on an easel and flanked by two police officers at a news conference.

The painting is a later work by the Austrian art nouveau master. Klimt painted it in 1916-17, and its disappearance had been one of the art world's biggest mysteries.

Since it's discovery, the work had been kept in a vault of a local branch of Italy's central bank.

This image taken from a video distributed Wednesday, Dec. 11, 2019 by Italian police shows two forensic police officers approaching a metal panel in which a painting was found, in Piacenza, northern Italy. A gardener at the Ricci Oddi modern art gallery in the northern city of Piacenza told Italian state TV on Tuesday that he was clearing ivy from the gallery's walls when he noticed a metal panel in which he found a bag inside a space within the walls. When the bag was opened it contained a painting that might be Klimt's “Portrait of a Lady,” which disappeared from the gallery during renovations in February 1997. (Italian Police via AP)

This image taken from a video distributed Wednesday, Dec. 11, 2019 by Italian police shows two forensic police officers approaching a metal panel in which a painting was found, in Piacenza, northern Italy. A gardener at the Ricci Oddi modern art gallery in the northern city of Piacenza told Italian state TV on Tuesday that he was clearing ivy from the gallery's walls when he noticed a metal panel in which he found a bag inside a space within the walls. When the bag was opened it contained a painting that might be Klimt's “Portrait of a Lady,” which disappeared from the gallery during renovations in February 1997. (Italian Police via AP)
This image taken from a video distributed Wednesday, Dec. 11, 2019 by Italian police shows an unidentified man showing a police officer a metal panel in which a painting was found, in Piacenza, northern Italy. A gardener at the Ricci Oddi modern art gallery in the northern city of Piacenza told Italian state TV on Tuesday that he was clearing ivy from the gallery's walls when he noticed a metal panel in which he found a bag inside a space within the walls. When the bag was opened it contained a painting that might be Klimt's “Portrait of a Lady,” which disappeared from the gallery during renovations in February 1997. (Italian Police via AP)

This image taken from a video distributed Wednesday, Dec. 11, 2019 by Italian police shows an unidentified man showing a police officer a metal panel in which a painting was found, in Piacenza, northern Italy. A gardener at the Ricci Oddi modern art gallery in the northern city of Piacenza told Italian state TV on Tuesday that he was clearing ivy from the gallery's walls when he noticed a metal panel in which he found a bag inside a space within the walls. When the bag was opened it contained a painting that might be Klimt's “Portrait of a Lady,” which disappeared from the gallery during renovations in February 1997. (Italian Police via AP)