By Dan Griffiths
BBC News, Beijing
China's leaders have long dreamed of taming the mighty Yangtze River.
The founder of the Chinese Republic, Sun Yatsen, first proposed the idea as a response to the flooding which has blighted the lives of those living along the river for thousands of years.
Chairman Mao wrote a poem in which he described a "great wall of stone" that would mean "a smooth lake rises in the narrow gorges".
But work on a dam did not actually begin until 1993 under then President Jiang Zemin.
And with the main wall of the Three Gorges Dam now finished, the dream is getting closer all the time. The wall stretches for more than 2km across the Yangtze and is the largest part of this multi-billion dollar scheme.
It is not the end of the project - there are still turbines and other equipment to be installed - but it is a major milestone on the way to finishing the dam.
When it is finished it will be the largest hydro-electric power project in the world, its 26 generators pumping out 85bn kW-hours of electricity a year.
Construction may be drawing to a close after 13 years but that is unlikely to stop the controversy about building the Three Gorges Dam in the first place.
Critics say the human cost has been far too high. More than a million people have been moved to make way for the dam.
At least 1,200 towns and villages will be submerged under the rising waters of the dam's reservoir.
The government says those who have been relocated will have new homes, jobs and compensation.
But many locals say corrupt officials have taken their money and they cannot make a living. Although the authorities say they have investigated and prosecuted many officials, the problem still persists.
Environmental campaigners say that an area of outstanding natural beauty will be lost to the world forever under the waters of the Three Gorges.
And they warn that the reservoir behind the dam is already severely polluted and likely to get worse as much of the waste from big cities upstream like Chongqing flow into the Yangtze.
Activist Dai Qing says the dam is causing more problems than solutions, insisting: "The electricity produced by the dam is much more expensive than that produced in other ways, because it costs tons of money to relocate local people and to offset the disasters it has caused to build the dam."
Important archaeological sites will be submerged
The Chinese government says it is spending billions of dollars on sewage treatment facilities. And it is pressing ahead regardless of the critics.
China desperately needs electricity for its booming economy. Power shortages are common now in many cities during the summer.
That is when millions of Chinese across the country switch on their air conditioners to cool down during the baking heat.
So the Three Gorges is part of China's energy strategy. The authorities also hope the dam will help control flooding on the Yangtze which in the past has claimed hundreds of thousands of lives and in recent years, caused millions of dollars worth of damage.
And the government has plans to build more dams on the Yangtze and other rivers across China.
These vast structures have become symbolic not only of China's engineering and construction capabilities but also of the Communist Party's desire for economic progress regardless of the human or environmental cost.
THE THREE GORGES DAM
Type: Concrete Gravity Dam
Cost: Official cost $25bn - actual cost believed to be much higher
Work began: 1993
Due for completion: 2009
Power generation: 26 turbines on left and right sides of dam. Six underground turbines planned for 2010
Power output: 49 billion kilowatt-hours
Reservoir: 660km long, submerging 632 sq km of land. When fully flooded, water will be 175m above sea level
Navigation: Two-way lock system became operational in 2004. One-step ship elevator due to open in 2009.