This jigsaw puzzle features one of the world's most impressive wonders - The Great Wall of China. The Wall is a series of fortifications made of stone, tamped earth, brick, wood, and other materials, built along an east-to-west line across the historical northern borders of China to protect the Chinese Empire against intrusions by various nomadic groups or military forces. The Great Wall stretches from Shanhaiguan in the east, to Lop Lake in the west, along an arc that roughly delineates the southern edge of Inner Mongolia. A comprehensive archaeological survey, using advanced technologies, has concluded that the Ming walls measure 8,850 km. Before the use of bricks, the Great Wall was mainly built from rammed earth, stones, and wood. During the Ming Dynasty, however, bricks were heavily used in many areas of the wall, as were materials such as tiles, lime, and stone.