I had expected to feel awe as I approached the Meridian Gate guarding what most Chinese call the Great Within—Beijing's Forbidden City—but I'm surprised to feel apprehension, too. After all, it's been a while since the emperors who ruled from behind these formidable walls casually snuffed out lesser lives by the thousands. From 1421 to 1912, this was the world's most magnificent command center—a reputed 9,999 rooms filled with nearly a million art treasures spread over 178 walled and moated acres.

Had I accompanied the Italian Jesuit Matteo Ricci, the first Westerner to visit the Forbidden City, in 1601, I would have seen these pavilions, courtyards and alleyways bustling with courtiers: concubines clad in silk, gold and jade; eunuchs serving as cooks, cleaners, clerks, compilers and companions; and the emperor's hard-eyed troopers bearing curved swords. But when I first visited, in 1973, not a single human voice sullied the silence, though the cawing of crows sounded like warnings and I thought the breeze playing about my ears could be the whispers of emperors past. I spent that first day 35 years ago treading the ancient clay bricks and marveling at the long procession of scarlet pavilions. Most were locked, and there were no guides to tell me their secrets. Mao Zedong was then putting China through his Cultural Revolution, and he had virtually closed the entire nation to outsiders. He had also sent the intellectuals—including, I assumed, the Forbidden City's guides—out to the countryside to toil with peasants in order to clean the dung from their overintellectualized brains.

I fell in love with the Forbidden City that long-ago day, and over the next 18 months visited it often. Back then, I was frustrated by how much of it was off-limits. But when I returned recently for three weeks of indulgent exploration, its formerly hidden glories were revealed.

Mao's capital was still a backwater in 1973, when I was the first Australian journalist to be based in Communist-ruled Beijing. Today, it is the capital of an emerging economic colossus. The ramshackle airport terminal I knew so well traffics in charter flights and gathers weeds, while a new one, completed in 1980, disgorges tens of thousands of visitors every day. (A big, brassy addition is slated to open before China hosts the Olympic Games in August.) In 1973, a crumbling two-lane road led through run-down villages and past carts hauled by donkeys (and men) to the capital, some 15 miles away. Now, an eight-lane highway carries shiny Toyotas and Mercedes-Benzes into the heart of Beijing.

Back in 1973, no more than a thousand cars navigated Beijing's potholed roads; now, my taxi driver tells me, there are more than two million. I look in vain for the ancient landmarks that dominated the once-graceful city center, but they have been obscured, or worse, by high-rise apartments, flashy hotels and shopping malls. In its latest great leap forward, the government has targeted the economy to quadruple by 2020. By 2040, many predict, China will have the world's largest economy. If, in this frenzied dash for wealth and influence, much of the old capital has been demolished, at least Tiananmen, the massive square fronting the Gate of Heavenly Peace south of the Forbidden City, remains. In 1989 the square was the site of antigovernment protests that left hundreds dead (estimates range from 200 to 3,000 or more), but now it is much as I remember it. Mao may have been responsible for more than 40 million deaths, but his portrait still hangs in a place of honor above the giant gateway. And his mummified body lies in an eerie mausoleum in the square.

From Tiananmen, one can glimpse the Forbidden City beyond the gate—pavilions roofed in yellow tiles and pagodas that only hint at the opulence inside. To my eye, the complex's luster is being tarnished, or rather tarted up, by ill-conceived restoration efforts: in one of the larger squares, masons are replacing ancient bricks with sheets of pale-gray slate, and outside many prominent pavilions, painters are slathering glossy paint over the traditional ocher-based flat finishes, which absorb light and gave the place an ageless look. But the scale and purpose of the Forbidden City still echo through the centuries. The Yongle emperor, son of the Ming dynasty's founder, commissioned the complex in 1406, choosing the spot where, a century and a half before, the Mongol ruler Kublai Khan had set his fabled winter capital, Khanbalik. According to the book Forbidden City, by the British Sinologist Frances Wood, a hundred thousand craftsmen and a million laborers and convicts toiled three years to create this earthly paradise, which the emperor's court occupied in 1421.

Once through the Meridian Gate, I am surrounded by a sea of humankind, with myriad accents and languages identifying visitors from all over China and the world beyond, but the grandeur of the place seems to need no translation. "As the Son of Heaven, the emperor's most important duty was to keep the balance between Heaven and Earth," says Yang Xin, 86, a professor of philosophy at what is still officially known as Peking University. "To help him achieve this, the Forbidden City was designed as a small model of the entire cosmos."

Its planners, following more than a thousand years of imperial tradition to convey a sense of harmony, set the most important buildings on a north-south axis and symmetrically flanked them with lesser structures. The Meridian Gate, U-shaped and with high red walls, was designed to heighten visitors' anticipation of being in the emperor's presence, Yang told me. Passing through a high vaulted passageway, I suddenly see five white stone bridges crossing a stream in front of a plaza that my guide says could hold 50,000 courtiers. Above the square hovers the 15th-century Hall of Supreme Harmony, at 120 feet the tallest building in the complex. "All important ceremonies were held in the square or in the hall," Yang said. "The emperor was married here, ascended the throne here, celebrated the New Year here and dispatched generals to fight wars from here."

In this square, on ceremonial days, a royal deputy would command tens of thousands of courtiers and military officers to ke tou to the emperor, seated out of sight in the main hall. The massed subjects would fall to their knees and bow their heads to the pavement nine times.

In 1793, Britain's first envoy to China, Lord Macartney, arrived to negotiate a trade treaty, bearing such gifts as air guns, a 25-foot-tall clock, a hot air balloon, telescopes and a planetarium. But when he was presented to Emperor Qianlong, he declined to "kowtow"—to do so, he felt, would demean Britain's ruling king, George III. After several meetings at which the emperor declined to talk business, he sent Macartney packing with a note: "We have never valued ingenious articles, nor do we have the slightest need of your country's manufactures," it read. "Our Celestial Empire possesses all things in prolific abundance and lacks no product within its own borders. There was therefore no need to import the manufactures of outside barbarians in exchange for our own produce."

It was under Qianlong, who reigned from the 1730s to the 1790s, that China extended its rule west to what is now Xinjiang province and south to Tibet, doubling its territory and becoming the world's richest and most populous nation. He appointed the Tibetan religious leader, the Dalai Lama, as a tributary ruler and protected him with Chinese troops. "Qianlong was not only a great warrior, but also a great painter and poet," says Yuan Hongqi, a deputy director of the Palace Museum. "He's my favorite emperor."

Mine, too. When he was 65, Qianlong finished building a retirement palace and garden of his own design, but he held on to the throne for another 20 years. As it happens, during my visit the Palace Museum and the World Monuments Fund announce a major restoration of the garden with help from Smithsonian Museum Conservation Institute experts, to be completed in 2016.

The Hall of Supreme Harmony, where emperors conducted affairs of state, is by general consent the most magnificent building in all of the Forbidden City. In constructing it, its builders relied on cosmology and feng shui (literally, "wind and water"), the belief that orientation and environment wield good and bad influences. The builders also believed the numbers nine and five to be auspicious. So the trained eye sees many combinations of nine, from passageways leading to squares, to golden knobs decorating giant doors—nine across, nine down—to the famed Nine Dragon Screen. (And remember those 9,999 rooms?) Erected in 1771, the screen is 95 feet long and 12 feet high. Its 270 glazed tiles form nine five-clawed dragons set against a backdrop of roiling clouds and sea. "Five is important because it's midway between one and nine," says Professor Yang. "So the imperial dragons have five claws, while all other dragons have three."

The dragon represented imperial traits: benevolence, excellence, boldness, heroism, perseverance, nobility and divinity. And so dragons are everywhere. Two perch on the roof of the Hall of Supreme Harmony, and 1,142 marble dragons' heads disguise the downspouts at its base. A marble ramp carved with dragons leads to the hall, where there are more dragons inside—13,844, to be precise—adorning columns, screens, walls, eaves and ceiling. More still run rampant over the Dragon Throne, while above it a painted dragon plays with a giant mock pearl. When I ask Li Ji, the Palace Museum's executive deputy director, just how many dragons there are in the Forbidden City, he gestures helplessly. "Too many to count," he says.

Beyond two other impressive pavilions—the Hall of Central Harmony and the Hall of Preserving Harmony—a pair of golden lions stand guard at the Gate of Heavenly Purity, the entrance to the emperor's private quarters, which is surrounded by high red walls. Next to the entranceway I see, improbably, a Starbucks in a building in which officials once waited to see the emperor. (The coffee emporium has since closed, after a Chinese blogger stoked widespread opposition to the franchise.) More modest pavilions once housed imperial concubines.

"The emperor chose his night companion from nameplates presented to him by a eunuch," says Yuan. A high-ranking eunuch, the Chief of the Imperial Bedchamber, would remove the woman's clothes to ensure that she carried no weapons or poisons, roll her up in a quilt and carry her on his back through the courtyards to the emperor.

During the Qing dynasty (1644-1912), only Manchu girls were eligible to become the emperor's concubines. (Manchus, warlike nomads from the northern steppes, made up just 2 percent of China's population yet ruled the country.) Typically, the empress dowager—the emperor's mother—led the selection process. In a famous 18th-century Chinese novel, Dream of a Red Mansion, an imperial concubine reflects on her pampered servitude: "How much happier are those whose home is a hut in a field, who eat salt and pickles and wear clothes of cotton, than she is who is endowed with wealth and rank, but separated from her flesh and blood."

Passions and ambitions stewed in this world within a world. In Chinese lore, more than 200 concubines died on the orders of the 16th-century emperor Shizong. Seeking to end their misery, 16 members of his harem stole into his bedchamber one night to strangle him with a silken cord and stab him with a hairpin. The emperor lost an eye in the struggle, but the empress saved his life. Court executioners then tore the limbs from the concubines and displayed their severed heads on poles.

Concubines often developed close attachments to the eunuchs, whose role as royal servants in China long preceded the building of the Forbidden City. In his autobiography, Emperor Puyi wrote that eunuchs at the court "were most numerous during the Ming dynasty (1368-1644) when they reached a strength of 100,000," but that number had dwindled to about 3,000 by the time Puyi became emperor, in 1908. The eunuchs, castrated to prevent nonimperial pregnancies among the concubines, tended to know their master's weaknesses and were often willing to exploit them. "The emperor in many cases became the plaything of those pariahs from the normal world," writes Taisuke Mitamura in Chinese Eunuchs: The Structure of Intimate Politics. "They deftly colored for their own purposes the ruler's picture of the outside world and turned him against any ministers who tried to oppose their influence."

Most eunuchs had chosen their way of life, says Yuan. "It seemed a little thing to give up one pleasure for so many," an unnamed eunuch told the British Sinologist John Blofeld in City of Lingering Splendour, Blofeld's memoir of early 20th-century Beijing. "My parents were poor, yet suffering that small change, I could be sure of an easy life in surroundings of great beauty and magnificence; I could aspire to intimate companionship with lovely women unmarred by their fear or distrust of me. I could even hope for power and wealth of my own."

The eunuch Li Lienying aligned himself with China's most infamous concubine, Empress Dowager Cixi. Only the third ruling empress in China's two-millennium imperial history, Cixi was perceived as the power behind the Dragon Throne for some 47 years, until her death in 1908. Court gossip had it that she fell in love with Li Lienying, and that they conspired to murder her potential rivals; British journalists depicted her as a cunning, sexually depraved tyrant. But Sterling Seagrave writes in Dragon Lady, his 1992 biography of the empress, that "slandering Tzu Hsi (Cixi) became a literary game over the decades." Her reign coincided with the empire's tumultuous decline.

Cixi entered the Forbidden City as a concubine in 1851, at age 16, and delivered Emperor Xianfeng his only male heir five years later, Seagrave writes. After Xianfeng died in 1861, possibly from the effects of his extended debaucheries, her son, then 5, took the throne as Emperor Tongzhi; she was named an empress dowager and Tongzhi's co-regent. Tongzhi ruled as emperor for only two years before dying of smallpox or syphilis at age 18, and Cixi again served as regent—first when her 3-year-old nephew was named Emperor Guangxu, and again when, as an adult, he was nearly deposed for allying himself with a radical reform movement that failed. Just before she died in 1908, at age 72, Cixi arranged for Guangxu's nephew—her grandnephew—to be named the last emperor of China.

Her place in the Chinese imagination is suggested by the number of homegrown tourists I saw jockeying for camera position at a small stone well near the northern gate by the Palace of Peace and Longevity. The story goes that when European troops, in Beijing in 1900 to put down the Boxer Rebellion, threatened to attack the Forbidden City, Cixi summoned Guangxu and his favorite concubine, Zhen Fei, then ordered the palace evacuated. Zhen Fei begged for the emperor to stay behind and negotiate with the invaders. The empress, enraged at the so-called Pearl Concubine, ordered some eunuchs to get rid of her, which they supposedly did by throwing her down this well.

Seagrave writes that there is no evidence to support this "dark fable." And Cixi's great-great-nephew, Yehanara Gen Zheng, a Manchu nobleman, offers an alternative version. "The concubine was sharp-tongued and often stood up to Cixi, making her angry," he told me. "When they were about to flee from the foreign troops, the concubine said she'd remain within the Forbidden City. Cixi told her that the barbarians would rape her if she stayed, and that it was best if she escaped disgrace by throwing herself down the well. The concubine did just that." Whatever the truth—and from the size of the well I doubt both versions—Chinese visitors are drawn to it by the thousands.

Inside the imperial garden—trees and walkways, ponds and pavilions created for the emperors' private pleasure—gilded bronze elephants squat beneath twisted cypress tree trunks. I have never come here without thinking about Puyi, the subject of Bernardo Bertolucci's Academy Award-winning 1987 movie, The Last Emperor. Poor Puyi. Born in 1906, he was named emperor just before his third birthday; after revolution swept his domain, the forces that would establish the Republic of China forced him to abdicate when he was 6. The miscast ruler spent the next 12 years as a virtual prisoner; the garden was his sanctuary.

Run Qi Guo Bu Luo, Puyi's brother-in-law, consulted on the Bertolucci movie. At 96, he lives in a small apartment near the Forbidden City. "Puyi never wanted to be emperor," he told me. "His great wish was to go to England and study to be a teacher." But even after abdicating, he could not escape the perils of power. In his autobiography, Puyi writes that he was eating an apple at 9 a.m. on November 5, 1924, when Republican troops gave him three hours to vacate the Forbidden City. That afternoon, after signing a declaration that "the imperial title of the Hsuan Tung Emperor of the Great Ching is this day abolished in perpetuity," the Son of Heaven fled in a fleet of limousines.

Puyi moved to Tianjin, in northeastern China, then controlled by the Japanese. In 1932, the Japanese set him up as the ruler of Manchukuo, their puppet state in Manchuria. In the waning days of World War II, he was captured by Soviet forces, and in 1950 repatriated to what had become the People's Republic of China. After ten years in a reeducation camp, he worked for the government as an editor. Puyi died at age 61 in 1967 as the Cultural Revolution was getting underway.

The fervor of that revolt almost claimed the Forbidden City. The Red Guards, having plundered historical sites to further Mao's aim of effacing anything traditional, planned to sack the Forbidden City, too. But Premier Zhou En-lai ordered the gates closed and sent other troops to protect it, thus preserving, among so much else, the Gate of Heavenly Peace, where the chairman's portrait still hangs.

Paul Raffaele, a frequent contributor to the magazine, wrote about the ark of the covenant for the December 2007 issue.