Ancient Romans built their towns using astronomically aligned grids, an Italian study concludes.The research examines the orientation of virtually all Roman towns in Italy and is published on the arXiv physics website, which is maintained by Cornell University "It emerged that these towns were not laid out at random. On the contrary, they were planned following strong symbolic aspects, all linked to astronomy," says Professor Giulio Magli, of the mathematics department at Milan's Polytechnic University The research examined the orientation of some 38 towns in Italy and is part of a wider study published in Magli's bookMagli explains that ancient Roman writers, including Ovid and Plutarch, documented how the foundation of a new town took into account the flight of birds and astronomical references."However, the link between Roman towns and sky symbolism has never been fully nvestigated," Magli says.The Romans founded many towns, or colonies, especially during Rome's Republican period and the first Imperial period, roughly from the 5th century BC to the 1st century AD.Their layout, inspired by the so-called castrum or military camp, was always the same.The town consisted of a rectangle bounded by walls, with streets organised in a grid to form various residential quarters or insulae.Two main roads, called cardus and decumanus, crisscrossed the whole town. Their intersection was the centre of the social and religious life, while four main gates were placed at their ends."I did not take into consideration all the Roman towns, but only those in which at least the two main roads are still clearly discernible," Magli says.For instance, the study did not examine the orientation of Pompeii. Its two main roads are not obvious as the Romans later modified the town's layout.Among towns with two clear main roads, Magli looked at the orientation of grids' axes in relation to the movement of the rising Sun at the eastern horizon over the course of the year.He extracted this orientation from available archaeological maps or by using a precision magnetic compass on site."It emerged that the majority of Roman towns in Italy are aligned to sunrise, in relation to important sacred festivals or to the cardinal points," Magli says.Basically, there are only three towns orientated toward the north: Pesaro, Rimini and Senigallia. These three also lie relatively close to the west coast of central Italy.Only two towns in northern Italy, Verona and Vicenza, lie near the summer solstice sunrise line. They are geographically close and were founded in the same period.All the other studied towns are oriented either within 10° southeast of sunrise, or near the winter solstice sunrise."Given these results, we can say that Roman towns in Italy are not randomly oriented. This will help us understand what kind of astronomical knowledge the Romans had," Magli says.Dr Manuela Incerti, of Ferrara University 's architecture department, describes the findings as "interesting research"."It certainly opens the way to more extensive studies," she says.