Three Gorges Dam, China

The other numbers are ever mind-boggling: the $625 billion dam is roughly 1.4 miles (2.3 kilometers) long and 607 feet tall, five times larger than Hoover Dam on the Arizona-Nevada border, and, when all 26 turbines become operational in 2009, it will be able to produce 18,000 megawatts of electricity, twenty times the power of Hoover Dam. The reservoir will also make it possible for 10,000-ton freighters to enter China's interior, opening a region burgeoning with agricultural and manufactured products, and increasing commercial shipping access to China's cities.
The project also features a few more controversial numbers: it will submerge about 244 square miles (393 square kilometers) of land, which includes the three gorges that give the dam its name (the Qutang, Wu Xia, and Xiling) and dozens of architectural and cultural sites. More than 1 million people will have been relocated by the dam's completion.