US Edition Before an altar bearing wreaths of olive branches, flowers, and statues of Athena, Dionysus and Hermes, a crowd of initiates wearing brightly coloured ribbons around their heads raise their right hands and intone: "Hail Zeus."
Incense fills the tightly packed, candlelit room, and the windows give on to a balcony with a magnificent view of the floodlit Acropolis. To millions of visitors every year, the Parthenon is a beautiful fragment of history. To the devotees wrapping their tongues around hymns in ancient Greek, it is a living place of worship.
"It is a temple of Athena, whom we worship," said Panayiotis Kakkavas, a long-time believer. "We should be allowed to hold our ceremonies there."
But according to Mr Kakkavas and his fellow believers, Greece's Olympian heritage, from temples to the Games themselves, have been promoted across the world to turn a profit, while the snappily titled Greek Society of the Friends of the Ancient and Followers of the Religion of the 12 Gods, is forced to meet in secret.
"Greece makes so much money out of our gods," he said. "But we are not allowed to pray to them even for free."
Unlicensed and unloved in a country which thrives on its Olympian heritage but whose population is officially 98 per cent Orthodox Christian, those who continue to celebrate the gods of old are nervous about their religious profession.
"We estimate we number about 100,000 across Greece, but many people are scared to declare their beliefs," said Panayiotis Marinis, who leads the prayers but is called a teacher rather than a priest. "We have been leading a campaign to have our religion legalised for eight years."
Members claim the conservative sway of the Greek Orthodox Church has prevented their religion being recognised. "The Church believes only it knows the truth," said Aphrosini Marselou. "So gatherings like this are hard to find. If I told anyone at work my beliefs I would be fired."
This week, as the full moon rose and was eclipsed blood red in the night sky, these modern muses jammed a room in a flat in central Athens to sing of the Olympian gods.
They came bearing fruits and cakes, but wearing work clothes. Only the ribbons around their heads marked them out from their daytime roles as lawyers, doctors, writers or secretaries.
Across Greece worshippers meet every full moon and for events marking seasonal changes. But for special occasions the illicit ceremonies are not always as hidden as this one.
"Sometimes we have small ceremonies when a group of us will meet and go and perform on the ancient sites which are our temples," said Ms Marselou. "There we leave these clothes and dress properly in togas."