A mathematician at the University of Oxford has questioned a widely accepted belief about the Parthenon in Athens, suggesting that the optical illusions supposedly built into its design may not exist at all. Prof Alain Goriely used mathematical modeling to analyze the structure and found that the so-called optical corrections attributed to the Parthenon are either nonsensical or nearly invisible. This idea originally came from Vitruvius, a 1st-century Roman architect and engineer, who wrote about the Parthenon almost 400 years after it was built. His account has since become a commonly accepted fact, even being cited by modern AI chatbots. The base of the Parthenon, known as the stylobate, is slightly curved, rising about 6 centimeters in the center. According to Vitruvius, this curve was meant to counter an illusion that would make the base appear to sag in the middle. However, Goriely found no evidence to support this claim. He examined two proposed optical effects but found no proof that either would create the illusion Vitruvius described. One theory suggested that long horizontal lines can appear to sag in the middle, but this effect is not clearly visible in the Parthenon's base. Another theory linked the columns to the Hering illusion, where lines on a flat surface can seem bent when intersected by other lines. However, the Parthenon's columns are too straight to produce this effect, and there is no evidence it applies in three dimensions. Another common belief is that the slight bulge in the Parthenon's columns—called entasis—was designed to prevent them from looking too narrow in the middle. Goriely found no evidence for this illusion either. The columns only bulge by 18 millimeters, a change so minimal that it is barely noticeable from normal viewing distances. Goriely examined other supposed optical corrections and dismissed them as well. He believes the Parthenon's architects may have had different reasons for these design choices, such as preventing water from pooling or making the structure more visually appealing to ancient Greeks. The persistence of the myth, he suggests, may be due in part to the modern view of ancient Greece as a highly intelligent and innovative civilization. Frank Salmon, a professor of classical architecture at the University of Cambridge, has long been skeptical of Vitruvius's explanations, noting the risks of relying solely on his writings to understand ancient building practices.