In the 21st century, Zhuang Yu, an ancient book restorer, unexpectedly obtained a handwritten fragment from the Tang Dynasty called "The Records of Mountains and Valleys". The engineering code recorded in it was surprisingly consistent with the Qin Zhidao construction project two thousand years ago.
In 212 BC, the First Emperor ordered General Meng Tian to build a "straight road" from Xianyang to Jiuyuan in order to defend the Huns from the north - the world's earliest "highway", with mountains and valleys spanning 1,800 miles. It took two and a half years to complete, and not a single blade of grass grew for more than 2,000 years.
