The Doric order is recognised by its capital, of which the echinus is like a circular cushion rising from the top of the column to the square abacus on which rest the lintels. The echinus appears flat and splayed in early examples, deeper and with greater curve in later, more refined examples, and smaller and straight-sided in Hellenistc examples. A refinement of the Doric column is the entasis, a gentle convex swelling to the profile of the column, which prevents an optical illusion of concavity. This is more pronounced in earlier examples.