Hidden codes discovered within some the world's most celebrated works of art and literature seem to be cropping up everywhere nowadays. Last year secret images of human anatomy were discovered in Michelangelo's "The Creation of Adam," a hidden musical code was found written into Plato's "The Republic," and most recently a code of numbers and letters were identified within the eyes of Da Vinci's "Mona Lisa."

Now the "Mona Lisa" is in the spotlight again. A Queens University classics professor believes he has found clues that Da Vinci may have incorporated images inspired by famous Italian poets in the background of the masterpiece, according to Physorg.com.

When most people look at the "Mona Lisa," they are struck by her mysterious smile and cryptic gaze. They don't even think to wonder why Da Vinci chose to paint her in front of such an ordinary, drab background. But professor emeritus Ross Kilpatrick isn't most people.

"The composition of the 'Mona Lisa' is striking. Why does Leonardo have an attractive woman sitting on a balcony, while in the background there is an entirely different world that is vast and barren?" asked Kilpatrick. "What is the artist trying to say?"

As a classics expert, Kilpatrick knew that many Renaissance artists utilized a technique called "invention," whereby a famous passage from literature is incorporated into the art. In the case of this painting's background, Kilpatrick believes Leonardo is alluding to Horace's Ode 1. 22 ("Integer vitae") and two sonnets by Petrarch ("Canzoniere" CXLV, CLIX).

All three of those poems allude to a smiling young woman who inspires in her suitors the desire to love and follow her anywhere in the world, from damp mountains to arid deserts. To Kilpatrick's eye, Horace and Petrarch's descriptions fit the background of the "Mona Lisa" almost perfectly.

The theory is strengthened by the bridge seen in the background that has been widely identified as one from Petrarch's hometown of Arezzo. Furthermore, the work of both poets would have been read at the same time that Leonardo painted the "Mona Lisa." It's likely that Leonardo would have had some familiarity with their work.

"The 'Mona Lisa' was made at a time when great literature was well known. It was quoted, referenced and celebrated," said Kilpatrick.

So could this literary reference be part of a real-life Da Vinci code? Kilpatrick has made his case, publishing his findings in the Italian journal MEDICEA.