employing the original ka shafts from the King’s Chamber as exhaust ducts and drawing fresh air through the access passage. The number of daily visitors has been severely limited and airlines have been warned of a “no-fly” zone above the site.

Further reading

Pemberton, Delia. 1992. Ancient Egypt. San Francisco: Chronicle Books.

Stierlin, Henri, and Anne Stierlin. 1995. The Pharaohs, Master-Builders. Paris: Terrail.

Great Wall of China

The largest man-made structure in the world, the Great Wall once stretched more than 4,500 miles (7,300 kilometers) from the Jiayu Pass in Gansu Province in the west to the mouth of the Yalu River in Liaoning Province in the east. The ravages of time and vandalism have reduced it to 1,500 miles (2,400 kilometers). It has been called an “engineering marvel of stone, earth and brick.”

From 475 to 221 b.c., there were seven warring states in Chou dynasty, China—Qi, Chu, Han, Wei, Qin, Yan, and Zhao. The borders of the latter three were frequently plundered by the nomadic Xiongnu (Huns) and Donghu tribes, so they built high earth walls as a defense against them. For their part, the remaining states took similar action, fearing attacks from their capricious neighbors. Soon after he had unified China in 221 b.c., the first emperor, the despotic Ch’in Shi Huangdi, set about reinforcing his defenses against the Xiongnu by joining four earlier fragmentary walls and building new sections to extend them to 3,100 miles (5,000 kilometers). In 214 b.c. he sent General Meng Tien, with an army of 300,000 conscripted workers and countless prisoners, to the northern frontiers of his empire to begin the building the Great Wall. Garrisons of soldiers along the wall served a double purpose: they stood guard over the workers and defended the northern boundaries. Much of the Ch’in wall was constructed with dry-laid local stone, but in remote places, where stone was unavailable, the builders used earth, compacted in 4-inch-thick (10-centimeter) layers. Watch-towers were spaced two bow shots apart.

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Great Wall of China, 221 b.c.a.d. 1640. Detail of the Badaling section over mountainous terrain near Beijing. 1977 photograph.

Ch’in Shi Huangdi’s policies of heavy taxation and forced labor to pay for foreign wars, the Wall, and other extravagant public works inevitably created social unrest. When he died in 210 b.c., his empire collapsed. Following years of chaos, the Han dynasty (206 b.c.-a.d. 220) was founded. Under Wu-Di (reigned 140–87 b.c.), the Han expanded into southern China, Vietnam, and Korea and opened trade routes through the wilderness of central Asia to India, Persia, and the Western world. Wu-Di controlled the Xiongnu incursions by invading their lands south of the Gobi Desert and colonizing the region with his own people. That strategy, incidentally, forced the Huns to move westward, part of a chain reaction that eventually brought about the demise of the Roman Empire. To protect what he had gained, Wu-Di inaugurated the third major phase of the Great Wall. He restored the Ch’in wall—neglected for years, the