text: However, to defend against the northern Xiongnu nomadic tribes, who had beaten back repeated campaigns against them, he ordered new walls to connect the fortifications along the empire's northern frontier. Hundreds of thousands of workers were mobilized, and an unknown number died, to build this precursor to the current Great Wall of China. Transporting building materials was difficult, so builders always tried to use local materials: rock over mountain ranges, rammed earth over the plains. "Build and move on" was a guiding principle, implying that the Wall was not a permanently fixed border. There are no surviving records specifying the length and course of the Qin walls, which have largely eroded away over the centuries.
  Lingqu Canal
  In 214 BC the Emperor began the project of a major canal allowing water transport between north and south China, originally for military supplies. The canal, 34 kilometres in length, links two of China's major waterways, the Xiang River flowing into the Yangtze and the Li Jiang flowing into the Pearl River. The canal aided Qin's expansion to the south-west. It is considered one of the three great feats of ancient Chinese engineering, along with the Great Wall and the Sichuan Dujiangyan Irrigation System.
  Elixir of life
  As he grew old, Qin Shi Huang desperately sought the fabled elixir of life which supposedly confers immortality. In his obsessive quest, he fell prey to many fraudulent elixirs. He visited Zhifu Island three times in his search.
  In one case he sent Xu Fu, a Zhifu islander, with ships carrying hundreds of young men and women in search of the mystical Penglai mountain. They sought Anqi Sheng, a thousand-year-old magician who had supposedly invited Qin Shi Huang during a chance meeting during his travels. The expedition never returned, perhaps for fear of the consequences of failure. Legends claim that they reached Japan and colonized it.