And those architectural marvels rely on a unique construction material: pozzolanic concrete, a spectacularly durable material that gave Roman structures their incredible strength.

Even today, one of their structures – the Pantheon, still intact and nearly 2,000 years old – holds the record for the world's largest dome of unreinforced concrete.

The properties of this concrete have generally been attributed to its ingredients: pozzolana, a mix of volcanic ash – named after the Italian city of Pozzuoli, where a significant deposit of it can be found – and lime. When mixed with water, the two materials can react to produce strong concrete.

But that, as it turns out, is not the whole story. An international team of researchers led by the Massachusetts Institute of Technology (MIT) found that not only are the materials slightly different from what we may have thought, but the techniques used to mix them were also different.

The smoking guns were small, white chunks of lime that can be found in what seems to be otherwise well-mixed concrete. The presence of these chunks had previously been attributed to poor mixing or materials, but that did not make sense to materials scientist Admir Masic of MIT.

"The idea that the presence of these lime clasts was simply attributed to low quality control always bothered me," Masic said in a January 2023 statement.

"If the Romans put so much effort into making an outstanding construction material, following all of the detailed recipes that had been optimized over the course of many centuries, why would they put so little effort into ensuring the production of a well-mixed final product? There has to be more to this story."