3. The Great Wall of China

A symbol of China's historical detachment and sense of vulnerability, the Great Wall snakes through the Chinese landscape, over deserts, hills and plains, for more than 2,500 miles. Yet, despite its seemingly impregnable battlements, the wall was ultimately an ineffective barricade. In the 13th century it was breached by the ferocious onslaught of the Mongols and then in 17th century by the Manchu, helped by the decline of the Ming dynasty. Today, its dilapidated remains crumble across the rugged terrain of northern China and only select stations have been restored.

Fascinating Facts: One of the legends about the wall tells that, during the Ming dynasty, General Cai Kai was put in charge of building the section of wall at Huanghua, 40 miles north of Beijing. Word got back to the emperor that the general was taking too long over the task and wasting too much money. The unfortunate general was therefore executed. Later, when the Mongols mounted a concerted attack, General Cai Kai's efforts paid off; Huanghua was the only fortress that successfully warded off the enemy. Realizing his mistake, the emperor exhumed General Cai Kai's body and had it reburied with full honours near the part of the wall that he built.