Out in the world
Entasis
Are the columns of this Greek temple in Italy, about 2,500 years old, straight?
No: they are slightly fatter in the middle, on purpose.
Why? Perfectly straight columns seem to be thinner in the middle. The builders added the bulge to fool the eye into seeing them as straight.
Picture: Michael Johanning, CC BY-SA 3.0 · Wikipedia(opens in a new tab)