Which feature emphasizes the elegant proportions in classical columns?

The feature that emphasizes the elegant proportions in classical columns is entasis. Entasis refers to the slight curvature or swell that is incorporated into the column shaft, making it appear more visually appealing and proportionate. This design technique helps to counteract the optical illusion of concavity that can occur when viewing straight lines, particularly in taller columns. By adding this subtle bulge, entasis creates a sense of vitality and elegance, enhancing the overall aesthetic of classical architecture.

Fluting, while it contributes to the texture and decoration of columns, does not specifically address the proportions. Capitals serve as the decorative top of the column and can vary widely in style, but they do not influence the column's vertical form directly. The base of the column provides a supportive element but also does not impact the perception of proportion in the column shaft itself. Therefore, entasis uniquely fulfills the role of emphasizing the elegant proportions that characterize classical columns.