It was the ultimate pagan party: pederasty, animal sacrifice, worshipping Gods - and naked sport.
Athletes took an oath over freshly sacrificed boar, fearing they'd be smitten to ashes for wrongdoing.
They were, after all, standing beneath a menacing 13-metre high statue of Zeus, made of gold and ivory - one of the seven wonders of the ancient world.
Much of the ancient Olympics, from 776BC to 394AD, is sacred rituals over sport.
At Olympia, some 210 kilometres south-west of Athens, legend has it demigod Hercules paced out the running track and marked a start-line in the sand - the Olympics, started from scratch.
Legend also has it Greek Gods competed there. Over on the Hill of Kronos, rising to the stadium's north, Zeus wrestled his Titan father for control of the world.
Apollo beat Hermes in a running race and Ares, god of war, at boxing.
"It takes a serious leap of our modern imagination to remember that the pagan Olympic Games were devoted first to religion and only second to athletics," writes Tony Perrottet in The Naked Olympics.
"Every sporting contest was dedicated to Zeus and sacred rituals took up as much time as sports."
A replica of an ancient statue in front of the Acropolis Parthenon (AAP)
The setting was near the town of Ellis - it was King Iphitos of Ellis who first declared the Olympic Games in 776BC.
With Greece plagued by war, the king turned to the Delphic Oracle and was told the only way to end the curse was to celebrate athletic games at Olympia, about 65km from his city.
For 293 ancient Olympiads, the Games became famous - for religious rituals, debauched parties, and for Greece's best athletes who became a demigod with Olympic victory.
Tens of thousands of spectators flocked to the Olympic sanctuary, whose heart was the sacred grove of Zeus - a walled enclosure of six acres known as Altis.
The sanctuary had three temples dedicated to Zeus; between them were some 70 altars; statues and shrines; memorials and monuments.
The spectators camped outside the sanctuary, creating a tent city in what largely became unsanitary orgies.
There was no reliable water supply at the site.
Held every four years to coincide with the second full moon of the summer solstice, it was stinking hot.
Olympic-times, the campers turned dry river beds into open air latrines.
Makeshift wells of rotting garbage and bones of hundreds of sacrificial animals lured flies by the million.
Before each ancient Games, priests sacrificed at an altar to Zeus, The Averter of Flies. Still, they came.
So did the people.
Greeks considered it misfortune to live life without witnessing an Olympics - an event held until Christian emperors banned pagan festivals in 394AD.
"Of course you put up with it all because it is an unforgettable spectacle," Athenian philosopher Epictetus wrote late in the 1st Century.
Tent city became a round-the-clock bacchanal.
Sure, there was sport. But there was also drinking games, sideshow artists, beauty contests, Homer reading competitions, eating races, masseurs, erotic dancers, palm readers, astrologists, soap box orators, fire eaters.
Famous Greek writers told their new work, actors recited odes, painters sold their art - and all around them, parties. Prostitutes made a year's wage in five days, the more scholarly took boy lovers.
"It is no exaggeration to say that sex and athletics were always intertwined in Greece," Perrottet wrote.
"For the Greeks, it was almost a social duty for adult males to take adolescent boys as lovers.
"Theirs was a mentor-tutor relationship ... intellectuals regarded the bond as finer and purer than heterosexual love, which was fatally muddied by the woman's erratic emotions and the brute need to procreate."
Married women were banned - obliged to camp on the far side of the dry River Alpheus, which had a view of the stadium. The unmarried could move freely.
The finest Greek athletes had a swearing-in ceremony: face to face with judges beneath the towering Zeus statue, at the God's feet were sacrificed boar and a stone tablet warning perjurers they would be smitten.
The initial 13 Games had just a foot-race over 210 yards - a fleet-footed cook named Coroibo is the first Olympic champion, gaining instant demigod status and an olive wreath said to be cut by Hercules from a sacred tree.
Later, there was chariot racing - in 67AD judges accepted bribes from Roman Emperor Nero, who won first prize despite falling out of his vehicle and not completing the course.
But a concentration emerged, starting on the pentathlon - discus, javelin, long jump, running and wrestling.
According to ancient scholars, Jason and his Argonauts created the pentathlon. On his quest for the golden fleece, Jason wanted to find his crew's most versatile athlete, so he combined their five favourite sports.
An actress plays the High Priestess holding the Olympic Flame in front of Hera Temple in Ancient Olympia (AAP)
The athletes - not Jason's, the Greeks - competed nude.
Some authors say an Athenian runner's loincloth slipped during a race and he tripped, so elders proclaimed all athletes should perform naked.
Others say it began when Orsippos of Megara reckoned he could run faster without a loincloth and duly won the 720BC sprint.
Regardless, nudity appealed to the sheer exhibitionism of Greeks, who derided the pale and flabby.
Nudity also removed social rank.
From 404BC, coaches and trainers watched - naked. All because a married woman (remember, she's banned) slipped into the stadium dressed in a trainer's tunic to watch her son.
Her boy Pisirodos won. She jumped the fence, tunic got caught, exposed herself.
The ancient Games were mostly held over five days, with a rest day in the middle for the Greeks' most important national ceremony: 100 white oxen were sacrificed on a grand altar, coinciding with the full moon.
Then action resumed - later Games introduced a double-lap and a 24-lap race and false starters literally copped a whipping, and then came wrestling, boxing and the brutal pankration.
Wrestling had 16 contestants and no weight divisions. Oiled bodies covered in coloured powder, the victor would throw his opponent down three times.
In boxing, long leather thongs were wrapped around the hands and wrists, then softened with oil or animal fat.
No ring. No rounds. The fight continued until one boxer was knocked out, or admitted defeat. If that took too long, judges ordered them to take turns landing undefended blows.
The pankration was more brutal still. Introduced in 648BC, it blended wrestling and kickboxing and only two things were banned: eye-gouging and biting.
Then, the final-night feast. A closing ceremony, of sorts, where victors were hailed at a lavish banquet.
The champions would then be paraded back to home towns in four-horse chariots. There, they lived the life of demigods - showered with gifts, houses, cash and tax immunity.