An Iowa public art museum is hailing the startling discovery of a long-forgotten 16th century painting that may be worth millions.

Hoyt Sherman Place in Des Moines acquired Old Master painter Otto van Veen’s “Apollo and Venus” in the 1920s but never put it on display, WHO-TV reports.

Hoyt Sherman executive director Robert Warren was searching for Civil War flags in a little-used storeroom when he stumbled upon the painting, but he isn't sure how it got there.

“So the assumption was it was tucked away there either because it needed some repair work or the content, because it is a full backside nude of Venus de Milo and another cherub sans clothing,” he told Radio Iowa.

The radio station reported that van Veen is best known for being a teacher of Peter Paul Reubens.

Warren said van Veen paintings have sold for between $4 million and $17 million and believes “Apollo and Venus” could fetch as much. He is having an appraiser determine its value but there are no plans to sell it.

Van Veen paintings hang in every museum around the world, including the Louvre. The Metropolitan Museum of Art in New York City displayed it in the 1880s.

“Apollo and Venus,” which was painted between 1595 and 1600, has been restored since being found.

Hoyt Sherman wound up with the painting after the family that owned the artwork gifted it to the Des Moines Women’s Club.

Warren said museum visitors will be able to see the painting soon.