Centuries Ago, an Architect Characterized the Parthenon’s Curves as a Clever Optical Illusion. Now, a Mathematician Begs to Differ

Athens’ ancient Parthenon, the most famous of all Greek temples, looks like a perfectly rectangular structure, bolstered by Doric columns and topped with crumbled triangular friezes. In reality, the 2,500-year-old building contains almost no straight lines or right angles. People have long believed that Athenian architects gave the Parthenon subtle curves to create a consummately linear optical illusion.

But according to a study recently published in Royal Society Open Science, that assertion is “one of the oldest and most enduring myths in human history.” “It’s widely accepted that it was made this way on purpose,” study author Alain Goriely, a mathematician at the University of Oxford, tells New Scientist’s Chris Simms. The mathematician, who is experienced in applying math to biology and engineering, maintains that although these physical attributes exist in the Parthenon, they weren’t meant to trick the eye. The Parthenon’s stylobate, the top layer of its rectangular base, has “a slight deliberate upward curvature,” Goriely writes.

We know this because of careful measurements taken in the 19th century: The middle is a little over two inches higher than the sides. And that upward curve is detectable not only on the stylobate, but on the euthynteria—the upper foundations, located underground—and on the entablature, which sits atop the columns. The longstanding assumption is that these elements were purposefully curved because if the lines were straight, viewers would perceive them as sagging downward.

Neuroscientist Marge Livingstone, who researches visual perception at Harvard Medical School, tells New Scientist, “I think it must have been for drainage, just like on roads.” The myth about the Parthenon’s horizontal curvature can actually be traced to ancient times. In the first century B.C.E., the Roman architect Vitruvius asserted that the Parthenon’s designers knew its lines would appear to curve downward if they were perfectly straight. Vitruvius’ claim was absorbed into Parthenon lore.

Goriely isn’t the first to question it. Standing nearly 35 feet tall, each scored column bulges about an inch at its middle. People have long believed that this was to account for an optical illusion that, were they even, would make them seem narrower in the center.

Nonsense, Goriely contends. He writes, “The assertion that straight-sided shafts appear concave lacks empirical support, and, to my knowledge, no such illusion has ever been scientifically demonstrated.” Swollen columns are common among Doric temples like the Parthenon, but experts don’t know exactly why. Hurwit told PBS, “The slight swelling makes the columns seem to be tense; they seem to swell up to respond to the weight that they carry.