The Greek Architectural Order is a system of classical architecture that consists of three main orders: Doric, Ionic, and Corinthian. The Doric order is the oldest and simplest of the three orders, characterized by its heavy, plain columns and lack of a base. The Ionic order is more ornate than the Doric, featuring slender columns with a base and volutes at the top. The Corinthian order is the most elaborate of the three, featuring ornate capitals with acanthus leaves and other decorations.