Its best-known use is in certain orders of Classical columns that diminish in a very gentle curve, rather than in a straight line as they narrow going upward.

[2] It may be observed among Classical period Greek column designs, for example, in the Doric order temples in Segesta, Selinus, Agrigento, and Paestum.

Chinese carpenters of the Song Dynasty followed designs in the AD 1103 Yingzao Fashi (Treatise on Architectural Methods or State Building Standards) that specified straight columns or those with an entasis on the upper third of the shaft.

Entasis was often a feature of Inca walls and doorways to counteract the optical illusion that would make the openings appear narrower in their middles.

[4] The opposite effect, applying concave curves in order to narrow surfaces that otherwise would appear to bulge, is also found in architecture, as in the sloping or battered walls of some Tibetan and Bhutanese monasteries and fortresses.

[7] Some descriptions of entasis[9] state simply that the technique was an enhancement applied to the more primitive conical columns to make them appear more substantial.