When China shocked the world with the appearance of a mushroom cloud over the Lop Nur salt lake on October 16, 1964 -- 40 years ago on Saturday -- it was the fruit of arduous work at "Nuclear City" in northwestern Qinghai province.

"No ordinary people were allowed anywhere near this place," said Zhou Hongying, a woman who settled down among the vacated laboratories and dormitory buildings in Haibei prefecture after the researchers left a decade ago.

"It was a restricted zone where only people with military authorization had access," she said.

Once a bustling community of 30,000 scientists, soldiers and, initially, Soviet advisers, all that is now left of State Plant No. 221 -- the facility's official name -- is empty factory buildings and decrepit apartment blocks.

But four decades ago its capacity for arming China with weapons of mass destruction was considered such a threat that successive US administrations contemplated targeting it in pre-emptive strikes even if it meant starting World War III.

It was Communist strongman Mao Zedong who decided in the late 1950s that China, too, must have the bomb, giving the green light for one of the massive super-human projects that were defining features of his reign.

Three thousand shepherds were driven from their ancestral homes in the Haibei region to make room for what was destined to become China's foremost center for nuclear weapons development and production.

Grainy black-and-white photographs at an exhibition hall in Xihai, the capital of Haibei prefecture, show the urban, professorial types who moved here to help China's nuclear dream come true.

They were young men with horn-rimmed glasses and bow ties and even younger women with long braids, some serious and others smiling, but all appearing woefully unprepared for life on China's harsh northwestern frontier.

"They came from the big cities, Beijing and Shanghai, to settle down here in the middle of nowhere," said Geng Shengcun, a local driver. "They suffered a lot."

Disastrously, the beginning of activity at State Plant No. 221 coincided with a mass famine hitting China in the years from 1958 to 1960, when failed agricultural policies claimed the lives of an estimated 30 million nationwide.

"The three years of natural calamities brought great trouble for the research base," a caption at the photo exhibit explains, skirting the fact that the misery was largely man-made.

"The whole nation brought assistance in the form of millions of kilograms of soybean and 40,000 head of cattle and sheep, helping the research base get through this difficult period."

Despite the researchers' severe problems with adjusting to the new environment, State Plant No. 221 marked triumph after triumph in the mid-1960s.

Just 33 months after the atomic blast, efforts at the plant led to the explosion of China's first hydrogen bomb, giving it the nickname "The Two-Bomb Base".

The victory was all the sweeter because the Soviet Union had abruptly withdrawn its assistance to China's nuclear program as tensions between Beijing and Moscow snapped around 1960.

"Soviet leader Nikita Khrushchev had said China could not develop a nuclear bomb in 20 years' time," a caption at the photo exhibition says mockingly.

The exhibit and a nearby memorial are unapologetic in their praise of China's nuclear program, with images of mushroom clouds symbolizing scientific progress, rather than Armageddon.

Playing a minor role in the official history are the wives and children of the plant's staff, who made this place their home for generations.

But personal recollections are now surfacing in private conversations and on the Internet.

A woman surnamed Wang who was born in the "Nuclear City" in the 1970s described on a weblog how she had preserved "countless fond memories" from a childhood in the northwestern grasslands.

"Even though the buildings are in ruins, and the reservoir where we used to stroll has dried out, the steppe is still there," she said. "It opens its bosom wide to a weary traveler returning home."

But amid the rough natural beauty, State Plant No. 221 became a scene of human depravity when the Cultural Revolution hit it like a whirlwind in the decade beginning in 1966.

Radical political fervor descended on the scientific community, possibly explaining why China's nuclear program suddenly slowed down after the successful test of the hydrogen bomb.

"We won't make any progress unless we kill someone," was the slogan adopted by radicals at the research center, and the campaign to liquidate closet capitalists proceeded accordingly.

According to one historical account, 59 people at the plant were beaten to death or were forced to commit suicide after being stamped as "counter-revolutionaries".

The "Nuclear City" with its hardships and tragedies is a world long gone, but rights groups have claimed the atomic research that went on here for decades had severe consequences for the environment.

Locals who have no choice but to live amid the relics of China's first experiments with nuclear technology prefer to shrug off the concerns as groundless.

"Scientific teams arrive here from Beijing every year to measure radiation," said Liu Youli, a construction worker employed to renovate a section of the old research site while officials consider new uses.

"There's no danger here. Otherwise, why would the local government set up its office just down the street from here?"

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