Is this carved rock an ancient Roman board game?

A mysterious flat stone with a geometric pattern of straight lines carved into it may be a previously unknown Roman board game.

Thousands of simulations by artificial intelligence of how sliding stone or glass pieces could have marked the surface suggest it was an early example of a blocking game, a type not documented in Europe until several centuries later in the Middle Ages.

Writings and physical remains have revealed that the Romans played many board games. These include Ludus latrunculorum, or the game of soldiers, where the goal is to capture the other player’s pieces; Ludus duodecim scriptorum, which means the game of 12 signs and is often thought of as an ancestor of backgammon; and games like tic-tac-toe, or noughts and crosses, where you win by placing three symbols in a line on a grid.

However, there are likely to be many games we don’t know about because nothing was written about them, no traces have survived or we just don’t recognise them for what they are.

In the Roman Museum in Heerlen, the Netherlands, Walter Crist at Leiden University, also in the Netherlands, came across a flat stone measuring 212 by 145 millimetres with a geometric pattern carved on its upper face. It was found at the Roman town of Coriovallum, which is buried under present-day Heerlen, and the type of limestone it is made of was often imported from France for use in decorative elements on buildings between AD 250 and 476.

“I was a bit sceptical at first because it’s a pattern I had not seen before, so I asked the museum to have a closer look,” says Crist. He then found visible wear on the object’s surface consistent with if you were pushing stone game pieces along the carved lines.

The wear was uneven, though, with most of it on one particular diagonal line.

To see what could have led to this distinctive pattern, Crist and his colleagues used an AI play system known as Ludii, which pitted two AI agents against each other. It simulated thousands of games with different numbers of starting pieces and 130 rule variations from various ancient board games that have been played in Europe, including haretavl from Scandinavia and gioco dell’orso from Italy.

The results revealed that nine similar blocking games, in which the person with more pieces tries to block their opponent from moving, could have led to the distinctive wear, says Crist.

The team is tentatively calling the game Ludus Coriovalli, or the game from Coriovallum.

“I’m not convinced we can ever know for sure, but the analysis shows that this object certainly could be a game board,” says Tim Penn at the University of Reading, UK.

“It’s an interesting approach,” says Ulrich Schädler at the University of Fribourg in Switzerland. But he’s not convinced the object is a game board, because the geometric pattern seems imprecise and this is the only known instance of this pattern, when normally many versions of game boards are found.

Crist accepts that we may never know, but says it may have been a prototype game, or one that was normally played using marks scratched in the earth so no traces remain.

Blocking games in Europe are documented from the Middle Ages onwards, so if Ludus Coriovalli is a blocking game, it pushes the evidence back several centuries for people playing these games there. They may have existed earlier in South and East Asia, says Crist, and there seem to be some blocking-game-like patterns in Roman-era graffiti, but it is difficult to date those.

Combining archaeological and AI methods like this could provide glimpses of other mysterious ancient games, says Penn. Another possible game board, from the Roman legionary camp at Vindonissa in Switzerland, features markings that look like a square with an X inside it, with little holes where lines meet. “Maybe this kind of analysis could help cast new light on it,” says Penn.

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