The decorative stonework was originally highly coloured. The temple was dedicated to the Athena at that time, though construction continued until almost the beginning of the Peloponnesian War in 432. By the year 438, the sculptural decoration of the Doric metopes on the frieze above the exterior colonnade, and of the Ionic frieze around the upper portion of the walls of the cella, had been completed. The richness of the Parthenon's frieze and metope decoration is in agreement with the function of the temple as a treasury. In the opisthodomus (the back room of the cella) were stored the monetary contributions of the Delian League of which Athens was the leading member.

Metopes

The ninety-two metopes were carved in high relief, a practice employed until then only in treasuries (buildings used to keep votive gifts to the gods). According to the building records, the metope sculptures date to the years 446-440 BC. Their design is attributed to the sculptor Kalamis. The metopes of the east side of the Parthenon, above the main entrance, depict the Gigantomachy (mythical battles between the Olympian gods and the Giants). The metopes of the west end show Amazonomachy (mythical battle of the Athenians against the Amazons). The metopes of the south side—with the exception of the somewhat problematic metopes 13–20, now lost—show the Thessalian Centauromachy (battle of the Lapiths aided by Theseus against the half-man, half-horse Centaurs). On the north side of the Parthenon the metopes are poorly preserved, but the subject seems to be the sack of Troy.
The metopes present surviving traces of the Severe Style in the anatomy of the figures' heads, in the limitation of the corporal movements to the contours and not to the muscles, and in the presence of pronounced veins in the figures of the Centauromachy. Several of the metopes still remain on the building, but with the exception of those on the northern side, they are severely damaged. Some of them are located at the Acropolis Museum, others are in the British Museum and one can be seen at the Louvre Museum.

Frieze

The most characteristic feature in the architecture and decoration of the temple is the Ionic frieze running around the exterior walls of the cella. The bas-relief frieze was carved in situ; it is dated in 442BC-438 BC.
One interpretation is that it depicts an idealized version of the Panathenaic procession from the Dipylon Gate in the Kerameikos to the Acropolis. In this procession held every year, with a special procession taking place every four years, Athenians and foreigners were participating to honour the goddess Athena offering sacrifices and a new peplos (dress woven by selected noble Athenian girls called ergastines).
Phidias Showing the Frieze of the Parthenon to his Friends, 1868 painting by Lawrence Alma-Tadema
Phidias Showing the Frieze of the Parthenon to his Friends, 1868 painting by Lawrence Alma-Tadema
Joan Breton Connelly has recently argued for another interpretation of the Frieze, in which she attempts to prove that the iconography of the Frieze is based on Greek Mythology. This interpretation postulates that the scenes depict the sacrifice of Pandora, youngest daughter of Erechtheus to Athena. This human sacrifice was demanded by Athena to save the city from Eumolpus, king of Eleusis who had gathered an army to attack Athens.
Pediments
Pausanias, the 2nd century traveller, when he visited the Acropolis and saw the Parthenon, only mentioned briefly the sculptures of the pediments (gable ends) of the temple, reserving the majority of his description for the gold and ivory statue of the goddess inside.
East pediment
The East pediment narrates the birth of Athena from the head of her father, Zeus. According to Greek mythology Zeus gave birth to Athena after a terrible headache prompted him to summon Hephaestus’ (the god of fire and the forge) assistance. To alleviate the pain he ordered Hephaestus to strike him with his forging hammer, and when he did, Zeus’ head split open and out popped the goddess Athena in full armour. The sculptural arrangement depicts the moment of Athena’s birth.
Unfortunately, the center pieces of the pediment were destroyed before Jacques Carrey created drawings in 1674, so all reconstructions are subject to conjecture and speculation. The main Olympian gods must have stood around Zeus and Athena watching the wondrous event with Hephaestus and Hera probably near them. The Carrey drawings are instrumental in reconstructing the sculptural arrangement beyond the center figures to the north and south.[7]
West pediment
The west pediment faced the Propylaia and depicted the contest between Athena and Poseidon during their competition for the honor of becoming the city’s patron. Athena and Poseidon appear at the center of the composition, diverging from one another in strong diagonal forms with the goddess holding the olive tree and the god of the sea raising his trident to strike the earth. At their flanks they are framed by two active groups of horses pulling chariots, while a crowd of legendary personalities from Athenian mythology fills the space out to the acute corners of the pediment.
The work on the pediments lasted from 438 to 432 BC and the sculptures of the Parthenon pediments are some of the finest examples of classical Greek art. The figures are sculpted in natural movement with bodies full of vital energy that bursts through their flesh, as the flesh in turn bursts through their thin clothing. The thin chitons allow the body underneath to be revealed as the focus of the composition. The distinction between gods and humans is blurred in the conceptual interplay between the idealism and naturalism bestowed on the stone by the sculptors.[8]
Athena Parthenos
The only piece of sculpture from the Parthenon known to be from the hand of Pheidias[9] was the statue of Athena housed in the naos. This massive chryselephantine sculpture is now lost and known only from copies, vase painting, gems, literary descriptions and coins.