Pediments are a form of gable in classical architecture, usually of a triangular shape. Pediments are placed above the horizontal structure of the cornice (an elaborated lintel), or entablature if supported by columns. In ancient architecture, a wide and low triangular pediment (the side angles 12.5° to 16°) typically formed the top element of the portico of a Greek temple, a style continued in Roman temples. But large pediments were rare on other types of building before Renaissance architecture. For symmetric designs, it provides a center point and is often used to add grandness to entrances.
The cornice continues round the top of the pediment, as well as below it. The tympanum is the triangular area within the pediment, which is often decorated with a pedimental sculpture which may be freestanding or a relief sculpture. The tympanum may hold an inscription, or in modern times, a clock face.
Pediments are found in ancient Greek architecture as early as 580 BC, in the archaic Temple of Artemis, Corfu, which was probably one of the first. Variations of the pediment occur in later architectural styles such as Classical, Neoclassical and Baroque.
The pediment is found in classical Greek temples, Etruscan, Roman, Renaissance, Baroque, Rococo, Neoclassical and Beaux-Arts architecture. Greek temples, normally rectangular in plan, generally had a pediment at each end, but Roman temples, and subsequent revivals, often had only one, in both cases across the whole width of the main front or facade. The rear of the typical Roman temple was a blank wall, usually without columns, but often a full pediment above. This effectively divorced the pediment from the columns beneath it in the original temple front ensemble, and thereafter it was no longer consider necessary for a pediment to be above columns. The most famous example of the Greek scheme is the Parthenon, with two tympanums filled with large groups of sculpted figures. An extreme but very influential example of the Roman style is the Pantheon, Rome, where a portico with pediment fronts a circular temple.