Strewn across the gleaming black floor of the imperial harem like blood-stained butterflies pinned to a board, the beautiful young concubines in Beijing's Forbidden City appeared at first to be sleeping, but the crimson pools of blood around their silken robes told a different story.
The palace soldiers had shown no mercy in slaying these fragile creatures on that terrible night in 1421.
Acting on the orders of the Ming Emperor Yongle, one of the most feared despots in Chinese imperial history, they had wielded their swords to ensure no one survived.
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Tyrannical: Emperor Yongle locked up his concubine Lady Cui
Some of their innocent victims were as young as 13, but one horrified chronicler of the time described how they had been "rent, split, ripped and torn to shreds" alongside the servant girls and eunuchs who guarded them.
In all, it is said that 2,800 people were killed in the harem as the Emperor tried to suppress a sex scandal which threatened to humiliate him at what should have been the proudest moment of his reign.
Beijing was then full of foreign dignitaries who had been invited to the unveiling ceremony of the Forbidden City, the architectural wonder which is still the largest palace in the world.
In murdering all witnesses to the scandalous developments in his own harem, Yongle hoped to keep them secret for eternity, but now the tale of treachery and murderous intrigue which unfolded within the blood-red walls of his palace is told in a dramatic BBC documentary.
Drawing on long-forgotten chronicles translated into English for the first time, it shows how, just as today's Chinese government hopes the Olympics will lend their regime credibility, so the building of the Forbidden City was Yongle's attempt to legitimise his claim to be supreme ruler of all China.
In fact, he had no right to call himself emperor.
When his father, the first Ming emperor died in 1398, the true heir to the throne was Yongle's 20-year-old nephew, Jianwen.
But Yongle was 18 years older than Jianwen and an aggressive warrior who had successfully defended China's northern reaches against the Mongols.
Yongle believed his father should have given him the throne instead.
He was encouraged in this by an old soothsayer who appeared before him in a tavern.
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Lady Cui (pictured here in the BBC reconstruction)
He told Yongle he was the true "son of heaven" and said he would one day be emperor, but only when his beard reached his navel.
Three years later, once the superstitious Yongle had grown his beard, he led his forces to Nanjing, then the capital of China, to kill his young nephew.
At first, Jianwen believed he was safe behind Nanjing's unbreachable defences, but then he learned that one of his generals had betrayed him, opening the gates to the invaders.
Yongle's triumph seemed assured, but he hadn't reckoned on the intervention of his father, Hongwu, from beyond the grave.
Just as Jianwen was contemplating suicide rather than die at the hands of his bloodthirsty uncle, an old eunuch who had served under Hongwu scuttled in with an ancient vermilion box and placed it before him.
Anticipating Yongle's fury at being overlooked as his heir, the late emperor had instructed that the box be given to his grandson in case of such an attack.
It contained a map of secret passageways under the city, orange robes and a razor for Jianwen to shave his head so he could escape into the countryside disguised as a Buddhist monk.
As he fled, Jianwen ordered the palace be burnt to the ground, leaving his family to die inside rather than face his uncle's wrath.
The blackened bodies of the empress and their six-year-old son were found by Yongle and his men when the flames died down.
Alongside them was the corpse of a young man.
Although it was burnt beyond recognition, Yongle decided it must be Jianwen and declared himself emperor.
But rumours were circulating about a mysterious monk seen running from the city shortly before the fire.
From then on, Yongle was haunted by the possibility that Jianwen might return to claim his throne.
The bloodshed, which marked the rest of his reign, flowed from his determination to prove that, just as the soothsayer had said, he was heaven's chosen agent on Earth. (To this day, no one knows what became of Jianwen.)
His first step was to demand the official sanction of Nanjing's political elite, in particular its most respected scholar, Fang Xiaoru.
When the old man refused to draft a document supporting his succession, Yongle ordered his men to set about him with their swords, but Fang Xiaoru had the last word - literally.
As he lay dying on the palace floor, he drew the Chinese character for "usurper" in his own blood.
In retaliation for this, Yongle purged the capital of all his political opponents, killing tens of thousands of people.
To assert himself as the new and unassailable Emperor of China, he built a new capital in the province of Beijing, 550 miles to the north, where his support base was strongest.
At the heart of Beijing - the Mandarin word for northern capital - would be the palace complex of the Forbidden City.
With nearly 1,000 buildings and more than 9,000 rooms occupying 180 acres - five times as much land as Buckingham Palace - Yongle hoped this wondrous creation would show it had been built with divine approval.
The construction took 15 years, and more than a million people were press ganged into gathering building materials for the palace from every corner of the empire.
Up on the freezing plains of the north, great slabs of marble were hauled across ice.
If any were sub-standard, those responsible for finding them were beaten or executed.
There was great suffering, too, in the province of Szechuan, where unpaid workers were ordered deep into the uncharted forests to fell hundreds of thousands of giant timbers.
Hounded by Yongle's soldiers and beset by disease, wild animals and sheer exhaustion, only half made it out alive.
The survivors rolled the trees down mountain gullies and into rivers, where they floated on a 1,000-mile journey to Beijing - a trip that took as long as four years.
As the building materials inched towards the new capital, Yongle ordered that every brick, pillar and stair of the old palace in Nanjing should be measured to ensure the Forbidden City should be "higher, grander and more magnificent".
This task was delegated to a team of eunuchs who were believed to make the most loyal servants.
Keeping their severed "treasure parts" in a jar and prizing them as proof of their devotion to their master, the 3,000 eunuchs at Yongle's court were his most trusted lackeys.
In 1408, he sent his chief eunuch on an extraordinary mission to neighbouring Korea.
Since the emperor had a penchant for Korean women, he was to bring back virgins to stock the imperial harem - which would take up a quarter of the Forbidden City.
Afraid of displeasing his neighbour, the Korean king sent his officials across the land to find its purest and most becoming young women.
All pretty girls had to be reported to the authorities, and anyone who hid their daughters or cut off their hair to make them ugly was arrested and stripped of everything they owned.
Among the recruits was Lady Cui, the 14-year-old daughter of a Korean government official who was taken 600 miles from her home to Beijing to serve the emperor.
She never saw her family again and her incredible stories, recently translated from the original Mandarin, give us unprecedented insight into the secret world of the concubines.
Until the Forbidden Palace was completed, Lady Cui and hundreds of other courtesans were locked inside the imperial palace in Nanjing (rebuilt after the fire), where they were taught the art of love-making - reading textbooks and studying erotic paintings that showed them how to please the emperor.
Those who became favourites, like Lady Cui, could become women of wealth and influence in the ritualised world of the harem, but catching the emperor's eye was not easy.
A strict astrological calendar was in operation, ensuring the emperor was having sex with the right woman on the right day, depending upon the time and circumstances of their birth.
This was to ensure his love-making accorded with the wishes of heaven, but it meant a particular concubine might not be called to the imperial bed-chamber for many years, and some were never summoned at all.
This lack of contact with the emperor might explain why some concubines resorted to so-called "vegetarian" affairs with the eunuchs - the only men, or half-men, they saw from day to day.
Since the Chinese were pioneers of sex aids, these intensely emotional relationships may also have been partly physical, but - whatever their nature - they were forbidden.
They could also have catastrophic consequences, as was seen shortly after Yongle unveiled the Forbidden City on New Year's Day 1421.
This was the emperor's triumphant moment but, though he had festooned the palace with statues of magical beasts to ward off evil, he did not enjoy heaven's blessing for long.
As the foreign ambassadors who had travelled so far for the opening ceremony enjoyed Beijing's hospitality outside the palace walls in the coming weeks, those inside were luxuriating in their surroundings.
The concubines had never known such opulence, with departments run by the eunuchs catering to their every whim. There was a Department of Entertainment to organise festivals and parties for them, a Department of the Bathhouse to provide them with steaming water, and even a Department of Toilet Paper.
But for the concubines it was a gilded prison.
Though they wanted for nothing, they were forbidden to leave the harem and their every move was spied upon by a secret police force known as the Eastern Depot, run by senior eunuchs.
Shortly after the ceremony, the Eastern Depot told Yongle that one of his favourite concubines had committed suicide after being caught having a relationship with a eunuch.
Any suggestion that Yongle was not in complete control of his palace could encourage his political enemies, within and outside China, to think he was a weak ruler, so he took action.
Away from the gaze of his foreign visitors, the occupants of the harem were rounded up, marched to their bloody deaths and silenced for ever.
There is no mention of this in Yongle's official records, but although he managed to write the murders out of history, the gods appeared to have taken their vengeance on him, as is divulged in the memoirs of Lady Cui.
Her life was spared because she had been recuperating from illness in the old imperial palace at Nanjing at the time of the massacre, but she returned to the Forbidden City the next night in time to witness what had happened.
"There was such deep sorrow in the palace that thunder shook the three great halls," recalled Lady Cui.
"Lightning struck them and after all those years of toil, they all burned to the ground."
The blaze lit up the whole city and soon spread - reducing 250 buildings to ashes and burning scores of men and women alive.
The palace Yongle had covered with lucky charms seemed damned.
Questioning what he had done, and fearful that heaven was angry with him, he sank into depression and died in August 1424, a broken man.
In the dark world of the Forbidden City, where life could be snuffed out in an instant, Lady Cui had outlived the emperor, but there was a sickening footnote in her "marriage vows".
She must never be allowed to give herself to another man. There was only one way to ensure that.
On the day of Yongle's funeral, she made herself beautiful for her emperor one last time and then, along with 15 of his other favourite concubines and their servant girls, she was executed - hung from a noose of white silk in a quiet hall within the Forbidden City. She was just 30 years old.
After Yongle's death, his son, the new Emperor Hongxi, planned to abandon the ill-fated palace and move the capital back to Nanjing, but he died just one year into his reign.
The palace, it seemed, was cursed.
The three great halls lay in ruins for 15 years until the decision was taken to rebuild them.
The Forbidden City would serve 24 emperors before 1911 when revolutionaries stormed the palace to end imperial rule.
Thanks to the determination of their modern-day successors to bring China into the 21st century, international attention will soon focus not on the Forbidden City but on a new landmark - the "Bird's Nest" Olympic stadium, five miles away.
Like its historic neighbour, it has cost vast sums to build - and is said to have cost the lives of many construction workers.
If it's all to be worth it, China's rulers will have to hope they fare better than Emperor Yongle - the tyrant who was in power the last time Beijing set out to dazzle the world.
• Secrets Of The Forbidden City, directed by Mark Lewis, is on BBC2 on Saturday, May 10, at 7.30pm.