Construction of the Three Gorges Dam on the Yangtze River in central China. On 15 May 2006, Chinese engineers were pouring the last of the concrete to finish the construction of the massive dam, which is designed to provide flood control and to be the largest electricity-generating plant in the world. By 15 May 2006, the dam spanned the entire river, and a large reservoir had filled behind it to the northwest. White spray shoots through gates in the center portion of the dam. The former locks are much less prominent, and the new ones to the north appear as a linear arrangement of thin, blue rectangles. Photos courtesy of NASA.