China uses almost half the world's steel and about half of the world's cement/concrete. These engineering wonders are just some of the things that have been built with all the material. The Three Gorges Dam is the world's biggest hydroelectric dam. It is the biggest concrete structure in the world too. It cost about 56 billion US dollars to build. The dam's hydroelectric power plants became fully operational in 2012 and can produce 22 gigawatts of power.