(CNN) While repairing Hadrian's Wall in the third century, some Roman soldiers amused themselves with a secondary activity: carving explicit graffiti. Now, archaeologists are creating a 3D record of the ancient markings, before they're lost to erosion.

Hadrian's Wall, a 73-mile stone frontier barrier stretching across northern England, was completed in A.D. 128 for the Emperor Hadrian. In A.D. 207, the army conducted repairs at Gelt Woods in Cumbria, where they etched words and drawings into a sandstone quarry.

The graffiti etched into the Cumbrian quality includes personal details about the soldiers who created it.

The inscriptions, known as "The Written Rock of Gelt," were rediscovered in the 18th century. They include a caricature of a commanding officer, as well as names, ranks and military units of some of the soldiers.

Then, of course, there is the R-rated carving, depicting a certain anatomical feature still gleefully doodled on walls today.

According to Rob Collins, lecturer in archaeology at Newcastle University, the phallic inscription isn't unusual; in fact, he has catalogued 57 other examples along the wall to date. Because the carvings appear similar to the images "boys tend to scribble in textbooks or walls," he told CNN, "it is easy to project a similar meaning on the Roman examples."

Read More