In geology, any relatively flat surface of bedrock (exposed or lightly covered with soil or gravel) that occurs at the base of a mountain or as a plain having no associated mountain. Pediments are most conspicuous in basin-and-range-type desert areas throughout the world, but they also occur in humid areas. In the tropics, the surfaces tend to be covered with soil and obscured by vegetation. Many tropical river towns are situated on pediments, which offer easier building sites than the steep hillsides above or the river marshes below.
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The pediment is found in classical Greek temples, renaissance, and neo-classical architecture. A prominent example is the Parthenon, where it served as a palette for beautiful, intricate sculptural detail, in the Roman Pantheon no such sculpture was intended. This Architectural elements was developed in the architecture of ancient Greece. In Ancient Rome, the Renaissance, and later architectural revivals, the pediment was used as a non-structural element over windows, doors and aedicules.
A variant is the "segmental" pediment, where the normal angular slope of the raking cornice is replaced by one in the form of a segment of a circle, in the manner of a depressed arch. Both traditional and segmental pediments have "broken" and "open" forms. In the broken pediment the raking cornice is left open at the apex. The open pediment is open along the base – often used in Georgian style architecture. A further variant is the "Swan-necked" pediment, where the raking cornice is in the form of two S-shaped brackets. The decorations in the tympanum can extend through these openings, enriched with "Alto-relievo" sculpture, "tondo" paintings, mirrors or windows. These forms were adopted in Mannerist architecture, and applied to furniture designed, or inspired, by Thomas Chippendale.