Incorporating millions of man hours and billions of dollars, the 2,309-meter-long (yard) dam has given physical form to the airy visions of generations of politicians.

"It's impressive," said Yang Chenxi, a student visiting the dam near the city of Yichang in central China's Hubei province.

"Most Chinese are more proud of this than they are of the manned space program because this is actually something that can make a difference in their lives," she said.

Engineers say they and the workers -- many of them migrants from Yunnan province near China's border with Vietnam -- will hold a modest ceremony Saturday as the last crane-load of concrete is poured on top of the dam.

It will mark 13 years of unprecedented labour, although it will still be more than two years before the project becomes fully operational, as some equipment, including the last power generators, remain to be installed.

One of the world's great feats of engineering, it will be visited by masses of future tourists who will marvel at the great skill of early 21st-Century man -- or his grand folly.

For critics point out the ambitious project has already led to the evacuation of more than one million people, will inundate priceless natural and archeological wonders, and could prove to be an environmental disaster.

But Cao Guangjing, vice president of the China Yangtze Three Gorges Project Development Co. which oversees the 180-billion-yuan (22.5-billion-dollar) project, is in no doubt that the dam is worth the price.

"The advantages outweigh the disadvantages. They far outweigh them," he said. "I believe 100 percent in this project."

With this kind of enthusiasm, objections are shrugged off as slightly irrelevant irritants.

This goes for claims such as that not only is the dam built in an earthquake-prone area -- the reservoir's water masses will be so heavy that they can trigger their own tremors.

"It's never happened before in history that a reservoir caused an earthquake," said Cao.

"The worst than can happen in the Three Gorges area is an earthquake of force six on the Richter scale, and the dam is built to withstand force seven."

Supporters argue the dam will have three main benefits, including flood prevention, power generation and improved navigation on the Yangtze.

"Currently we have serious floods every 10 years," said Wang Xiaomao, deputy chief engineer at the Yangtze River Water Resources Committee. "With the dam, that will change to once every 100 years."

Even while work was being carried out on the dam, the engineers and laborers were reminded that flood control is one of the main reasons why the giant project is being undertaken.

In 1998, a devastating flood developed along the Yangtze, uprooting millions of families and killing more than 1,500. Two much larger disasters in the 1930s each claimed more than 140,000 lives.

Nevertheless, critics continue to argue that due to silt build-ups and other problems, the dam will fail to bring the flood relief that officials hope.

Harnessing the power of China's mightiest rivers is another dream harbored by generations of Chinese.

In the early 20th century, Dr Sun Yat-sen, the founder of modern China, waxed poetical about creating electricity that would be the equivalent of the strength of hundreds of millions of men.

It is no longer just the stuff of poetry. On the left bank, 14 sets of 700 megawatt turbine and generator units are already in operation.

On the right bank, 12 further 700 megawatt units are still under construction and installation.

With a capacity already equivalent to Itaipu, situated on the border of Brazil and Paraguay and currently the largest operating hydro-electric dam in the world, the Three Gorges will eventually overshadow all others.

A new tender process will be held by the end of the year for adding a new power station with a set of six more 700 megawatt generators, underground and next to that of the right bank.

The dam will hence become "the biggest in the world", according to the China Yangtze Three Gorges Project Corporation.

One final benefit of the project is that it will elevate the Yangtze for hundreds of kilometers inland, allowing ocean-going vessels to travel as far as the enormous, but little known metropolis of Chongqing.

This will, planners hope, help open up China's underdeveloped west, which has in many ways has missed out on economic reforms largely because of its isolation from overseas markets.

To ease navigation on the Yangtze upstream from the dam, a ship lift will enable vessels of up to 3,000 tonnes to pass the dam in 45 minutes, while a ship lock will do the same to 10,000-tonne vessels in two hours and 45 minutes.

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