Ancient Greek temples usually consist of a base with stairs at each edges (known as crepidoma), a cella (or naos) with a cult statue in it, columns, an entablature, and two pediments, one on the front side and another in the back. By the 4th century BC, Greek architects and stonemasons had developed a system of rules for all buildings known as the orders: the Doric, the Ionic, and the Corinthian. They are most easily recognised by their columns (especially by the capitals).