🏛️ Do the Parthenon’s lines really correct optical illusions?

The famous curves of the Parthenon may have been misunderstood for centuries.

The Greek temple, built in Athens in the fifth century BCE, is not made up solely of perfectly straight lines. Its base rises slightly toward the center. Its columns also display small variations in shape. A widely accepted explanation claims that the builders deliberately created these deviations to deceive our eyes.

The idea seems ingenious: without these corrections, some straight lines would appear curved or sagging. Mathematician Alain Goriely of the University of Oxford wanted to test this explanation. He studied the visual effects invoked and the monument’s actual dimensions.

First example: the temple’s base rises by about 6 cm toward its middle. According to an old theory, a perfectly horizontal base would appear to sag at the center. Yet the researcher found no solid evidence of this visual effect in this situation. The curvature of the Parthenon therefore cannot be presented with certainty as an optical correction.

The columns raise the same question. They bulge very slightly instead of forming perfectly straight lines. This variation reaches only about 18 mm. It is difficult to perceive from the usual viewing distances. Once again, the illusion that this shape was supposed to correct has not been established.

Another explanation invokes a known illusion: parallel lines can appear curved when other lines cross them. However, this effect depends strongly on their orientation. In the Parthenon, the columns are too close to vertical to produce the effect expected by this theory.

So where does this story come from? Goriely traces it in particular to Vitruvius, a Roman architect who wrote several centuries after the construction of the Parthenon. The explanation was then repeated in numerous works. In the nineteenth century, precise measurements of the temple’s curves further strengthened its popularity.

The study does not say why the Greeks chose these forms. Several reasons remain possible. A slightly domed base, for example, may facilitate water drainage. Some curves may also have resulted from aesthetic or construction choices. In the absence of contemporary texts explaining the builders’ intentions, the question remains open.