The Parthenon's design includes subtle curves and inclinations. Its columns and platform are more than a simple combination of straight lines, and these details affect the overall visual impression.
Built on the Acropolis of Athens, it was connected with the worship of Athena. It later underwent changes of religious use, war damage, and the dispersal of its sculptures.
Present building
In the mid-5th century BC, when the Athenian Acropolis became the seat of the Delian League, Pericles initiated the building project that lasted the entire second half of the century. The most important buildings visible on the Acropolis today – the Parthenon, the Propylaia, the Erechtheion and the Temple of Athena Nike – were erected during this period. The Parthenon was built under the general supervision of Phidias, who also had charge of the sculptural decoration. The architects Ictinos and Callicrates began their work in 447, and the building was substantially completed by 432. Work on the decorations continued until at least 431.
The Parthenon was built primarily by men who knew how to work marble. These quarrymen had exceptional skills and were able to cut the blocks of marble to very specific measurements. The quarrymen also knew how to avoid the faults, which were numerous in the Pentelic marble. If the marble blocks were not up to standard, the architects would reject them. The marble was worked with iron tools – picks, points, punches, chisels, and drills. The quarrymen would hold their tools against the marble block and firmly tap the surface of the rock.
A big project like the Parthenon attracted stonemasons from far and wide who travelled to Athens to assist in the project. Slaves and foreigners worked together with the Athenian citizens in the building of the Parthenon, doing the same jobs for the same pay. Temple building was a specialised craft, and there were not many men in Greece qualified to build temples like the Parthenon, so these men would travel and work where they were needed.
Optical refinements
The close measurement of the Parthenon in the nineteenth century revealed that the temple deviated from strict rectilinearity through several optical refinements. First, the stylobate is curved, bulging upward at the centre—by 10.3 cm over 70 m (a 1/700 ratio)—with a corresponding curvature in the entablature, visible as a slight ridge on the capitals. Second, the columns exhibit entasis, i.e., swelling that reduces toward the top, a practice in use by mid-6th century but in Parthenon the effect is subtler with a ratio of 1/550 to 1/600. Third, both the columns and naos walls incline slightly inward. Fourth, the corner columns are slightly displaced.
Scholars have proposed several explanations for the curvatures found in Parthenon. The primary explanation is based on the Optical Correction or Irradiance Theory, proposed in An Investigation of the Principles of Athenian Architecture by Francis Penrose in 1851. The theory asserts that convex adjustments were made to counteract the concave appearance silhouetted objects can have to the human eye. Others attribute the refinements to structural, such as drainage, or aesthetic considerations rather than perceptual ones. In 1878, John Pennethorne's The Geometry and Optics of Ancient Architecture argued that curvilinear nature of the Parthenon was a deliberate design choice, supporting Penrose's conclusions and corresponding with Vitruvius' account of the Scamilli impares. Karl Bötticher believed the deviations resulted from structural settlement, while William Henry Goodyear viewed them as symbolic and aesthetic.
Another refinement relates to the Doric order's angle, that is the challenge of spacing columns, metopes, and triglyphs so the frieze ends correctly at the corners, known as contraction problem. At the Parthenon, the architects to resolve this problem varied the length of the metopes, between 1.175 and 1.37 m, and 'overcontracting' the corner incolumnations.
The mathematician Alain Goriely in a paper titled "The illusion of illusions: there are no optical corrections in the Parthenon" has argued the claim of optical refinements is "one of the oldest and most enduring myths in human history", noting that they are "either unsupported by evidence or too small to have a perceptible effect under typical viewing conditions".