Peel back the layers of history (and drywall) from any old Parisian building and you are bound to strike upon some buried treasure. Still, it’s quite unusual for construction workers to uncover something as mammoth-sized as the 17th-century painting that renovators found inside Oscar de la Renta’s new Paris outpost.

Alex Bolen, the luxury retailer’s chief executive, tells The New York Times that behind one of his store walls was a monumental 10-by-20-foot oil painting of a debonaire 17th-century marquis and assorted courtiers traveling into the city of Jerusalem.

“It’s very rare and exceptional, for many reasons,” restoration specialist Benoît Janson, who is overseeing work on the canvas, told the publication. “Its historical and aesthetic quality and size” make it a brilliant outlier in the sea of smaller finds throughout the city.

“It was very dark because of all the overpaint from earlier restorations and varnish,” Janson also remarked of the painting’s conservation challenges. For the last two months, teams of three to five people have swabbed away at the canvas as more details have emerged: the hint of a mosque, the Western Wall, the gilded horses of French nobility.

After consulting with art historian Stephane Pinta, an expert in old-master paintings, it was determined that the work was likely completed in 1674 by Arnould de Veuz, a painter who worked with Charles Le Brun, the first painter to Louis XIV and designer of the Château de Versailles’ interiors. The artist’s reputation arguably preceded his work; De Veuz was known for entering duels of honor and was eventually forced to flee France for Constantinople.

How did Pinta come to such an attribution? He traced the painting to a plate that was reproduced in the 1900 book “Odyssey of an Ambassador: The Travels of the Marquis de Nointel, 1670-1680” by Albert Vandal, which told the story of the travels of Charles-Marie-François Olier, Marquis de Nointel et d’Angervilliers, Louis XIV’s ambassador to the Ottoman Court. On Page 129, there is a rotogravure of de Vuez’s detailed painting of Marquis de Nointel entering Jerusalem.

Experts with Oscar de la Renta are still stumped as to how the painting came to their site, or why it was attached to the wall with gauze and glue. There is speculation that it may have happened before the Nazi occupation of Paris during World War II; perhaps it was forgotten in the fog of war.

Along with the painting, renovators of the 19th-century building have uncovered decorative coffered ceilings with eight of the 29 inset squares featuring painted coats of arms. Before the boutique was gutted, Bolen had described the space as “pretty charmless.”

Zachary Small was a writer at Hyperallergic.