 The 600 km ( 370 mi ) long reservoir flooded some 1 @,@ 300 archaeological sites and altered the appearance of the Three Gorges as the water level rose over 300 ft ( 91 m ) . Cultural and historical relics are being moved to higher ground as they are discovered , but the flooding inevitably covered undiscovered relics . Some sites could not be moved because of their location , size , or design . For example , the hanging coffins site high in the Shen Nong Gorge is part of the cliffs . 
