What effect does Entasis have in classical architecture?

Entasis refers to the slight curvature or tapering that is applied to columns and other vertical elements in classical architecture. The primary purpose of entasis is to counteract the optical illusions of straight lines, particularly the way they can appear to bulge or sag. When a column is perfectly straight, it may visually seem to have irregularities due to the way our eyes perceive lines; therefore, the subtle curvature of entasis creates a visual effect that actually makes these structures appear more graceful and aligned. This counterbalance enhances the aesthetic of harmony and stability in architecture.

In contrast, the other options do not accurately describe the role of entasis. While it does not primarily enlarge structures or focus on decorative details, its foundational intent is to address the perception of straightness, ensuring that classical structures maintain a harmonious visual appeal.