Page "Acropolis of Athens" Paragraph 77

Every four years, the Athenians held a festival called the Panathenaea that rivaled the Olympic Games in popularity.

During the festival, a procession ( believed to be depicted on the Parthenon frieze ) traveled through the city via the Panathenaic Way and culminated on the Acropolis.

There, a new robe of woven wool ( peplos ) was placed on either the statue of Athena Polias in the Erechtheum ( during a regular Panathenaea ) or on the statue of Athena Parthenos in the Parthenon ( during the Great Panathenaea, held every four years ).