[4] Athenian myth recorded two synoecisms: first the establishment by King Cecrops of the original twelve cities of Attica, and then merger of these twelve cities into a single Athenian state by the mythological King Theseus, with its political centre in Athens.
The festival was organised and paid for by the phylobasileis, representatives of the original four Athenian tribes, which had otherwise fallen out of use after the reforms of Cleisthenes in 508 BC.
[5] After the Athenian victory over the Persians in the first Greco-Persian War and the subsequent rebuilding and resettling of the city-state, the Synoikia festival became even grander than before.
Some “Thesean elements [from] festivals…[were] infused with ceremonies belonging to [Athena, and vice versa]... even those not connected with the Synoikia.”[1] In 374 BC, in honour of a short-lived armistice during the Boeotian War, the Athenians added a “bloodless” sacrifice to Eirene, the goddess of peace.
[2][5] While this festival was celebrated by the Athenians, there were not many indications that showed that the other demes in Attica, outside of Athens, held Synoikia.