The Panathenaic Games were a set of games held every four years in Athens in Ancient Greece.
The games were actually part of a much larger religious festival, the Panathenaia, which was held every year. Every fourth year when the games were also held, the festival was known as the "Great Panathenaia," and was 3 or 4 days longer than the regular festival. They were the most prestigious games for the citizens of Athens, but they were not as important as the Olympic Games or the other Panhellenic Games.
The first Great Panathenaia was organized by Pisistratus in 566 BC, and was modelled on the Olympic Games. Pisistratus also added music and poetry competitions, which were part of the Nemean Games but not the Olympics. The games were divided into games for Athenians only, and games for Athenians and any other Greeks who wanted to participate. The games for all Greeks were essentially the same as the Olympics, with boxing, wrestling, pankration, pentathlon, and chariot racing, but chariot racing was the most prestigious of these, unlike the Olympics where the stadion (foot race) was more important. The winner of the chariot race received as a prize 140 amphorae full of olive oil.
The games in which only the Athenians were allowed to participate were somewhat different. These included a torch race to the Parthenon (the ancestor of the modern Olympic torch relay that takes place prior to the Games), mock infantry and cavalry battles, a javelin throw on horseback, the apobotai (a chariot race in which the driver had to jump out of the chariot, run alongside, and jump back in), the pyrriche (apparently military exercises accompanied by music), and the euandrion (essentially a beauty contest among the athletes). In later years there was also a rowing competition.
The procession to the Parthenon was, however, more important than the games themselves. During the Great Panathenaia (but not the regular Panathenaia held every year), a special robe (the peplos) was made by the women of Athens for the statue of Athena, which was carried to the Parthenon as part of the procession. There was also a large sacrifice made to Athena, and the meat from the sacrificed animals was used in an enormous banquet on the final day of the festival.