Watch Modern Marvels Season 7 Episode 23 Online

When completed, China’s Three Gorges Dam will tower 607 feet in the air and weigh 40 Great Pyramids. Other than China’s Great Wall, it will be the only man-made object visible from the moon. Supporters see it as key to a new China, controlling floods and bringing hydroelectric power to one of its least-developed areas. Critics voice a litany of concerns–from environmental to flooding the spectacular area for which it’s named. We trace its story–from ancient flood control to current controversy.