A stone from Roman times amazed experts. AI may have solved the mystery.

A smooth, white Roman-era stone unearthed in the Netherlands has long puzzled researchers.

With the help of artificial intelligence, scientists now believe they have solved the secret: The Stone is an ancient board game and they have even guessed the rules.

Diagonal and straight lines are cut into the circular piece of limestone.

Using 3D imaging, scientists discovered that some lines were deeper than others, suggesting that parts were moving along those lines, some more than others.

“We can see signs of wear along the lines on the stone, exactly where you would move a piece,” said Walter Crist, an archaeologist at Leiden University who specializes in ancient games.

Other researchers at Maastricht University then used an artificial intelligence program that can derive the rules of ancient games.

They trained this AI, named Ludii, with the rules of about 100 ancient…