One of most original paintings of the 15th century, the mural covers the vault and walls of the Sala delle Asse in the Sforza Castle in Milan. It depicts a garden pergola made of 16 mulberry trees bound together by a golden, knotted rope. The trunk of each tree rises as a column supporting 16 half-moon-shaped spaces above a Gothic vault, producing an evocative, fictive grove.

Now restorers might be able to bring to light extra sections of the original work, possibly providing further insights into Da Vinci’s vision of the highly symbolic decoration.

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The work was commissioned in 1498 by the duke of Milan, Ludovico Maria Sforza, nicknamed il Moro (the Moor) and was executed by Leonardo, who at that time was the court artist, and his assistants.

Experts agree the master’s hand can be detected in a monochrome section of the fresco on the northeast and northwest corner of the room. The apparently unfinished work depicts sturdy roots bursting through rocks.

“Large parts of this mural can be recovered beneath several layers of whitewash,” the Opificio Pietre Dure (OPD) the Florence based institute who is carrying out the restoration, wrote in a report.

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Preliminary analysis produced “quite interesting results,” lending hope that the work will recover “important parts of the preparatory drawings,” Marco Ciatti, superintendent of the OPD art restoration institute, said.

Leonardo’s work in the Sala delle Asse, or Room of the Planks (after the wood panels that lined it) has remained largely unknown. In 1499 Milan was conquered by the French who stormed the castle. In 1706, when Milan was under the Austrian rule, the castle became soldier barracks and the Sala delle Asse was turned into a stable, its walls covered with abundant layers of whitewash.

The arboreal decoration remained hidden beneath up to 13 layers of paint until 1893, when renovations to the castle revealed traces of frescoes.

In 1901, amid much criticism, the mural was heavily restored.

Only in 1954, the paint applied during the disastrous restoration was finally removed. But damage to Leonardo’s work remained.

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“The mural is covered by a thick layer of grime. However, our cleaning tests indicate that it can be easily removed. Leonardo’s paint won’t be damaged in the procedure,” the restorers wrote.

Meanwhile, archival research also revealed the room’s original name.

It was called “Camera dei Moroni” — a clear allusion to Ludovico il Moro.

Indeed Leonardo’s decoration is filled with punning allusions. The mulberry, or Morus tree, refers to the Duke’s well known nickname, Il Moro, the Moor. The tree is also a symbol for the Milanese silk industry – mulberries were cultivated in the region as food for the silkworm.

“This restoration is extremely important to fully understand Leonardo’s work,” Milan culture councillor Filippo Del Corno said. “The project will last two years, ending just in time for the Milan’s Expo 2015,” he added.