In pictures: Three Gorges Dam

The Olympic torch relay has reached Yichang, near the three magnificent valleys, universally known as the Three Gorges, where the Yangtze river snakes through the Daba Mountains.

The region is home to the Three Gorges Dam, the largest hydro-electric power project in the world. Dubbed the biggest engineering feat since the Great Wall, it has taken shape over the last 16 years.

The dam has spawned a reservoir 660 km (410 miles) long and about 1km wide, displaced millions of people and submerged many cultural heritage sites.

Environmental groups say the project has wreaked havoc in the region, bringing pollution, soil erosion and landslides, as well as blocking fish migratory routes along the world's third longest river.

But officials believe the benefits outweigh the costs. When its 6,000-tonne turbines begin work - scheduled for next year - they will produce enough electricity to power a sizeable city.

China points out the dam will generate non-polluting power and stop the Yangtze valley flooding, a problem that claimed the lives of an estimated nearly one million people during the 20th Century.

Scientists have claimed the weight of water from the dam reservoir will be so heavy it could even tilt the Earth on its rotational axis by a slight degree, though this will be imperceptible to humans.