With a total length of 21196.18 kilometers (including 6,259.6 kilometers of artificial walls), the Great Wall represents the wisdom of the Chinese nation developed since ancient times. It has been a mute witness of Chinese history stretching back more than two millennia. It is the largest ancient defense pro- ject constructed over the longest span of time. Since there was a historical record of the two Chinese characters Chang Cheng (Great Wall) in the Spring and Autumn Period (770-476 BCE), the work of building and maintaining it has been a continuous process for well over two thousand years encompass- ing vast areas of north and central China. The Great Wall bears the precious historical memory and national spirit of the Chinese nation. With the passage of time, many sections along its 5,000- km length have been destroyed, although the names remain. Sections of the Great Wall extant today, known almost to all, include Badaling, Shanhaiguan and Jiayuguan. We hope this book can bring readers different experiences of an Earth- based structure visible. The areas bisected by it include deserts and grass- lands, rivers and the remains of enemy towers. May the words recorded here make it possible for readers to gain a better understanding of this world his- torical heritage site.