https://goo.gl/images/Ewfg2P By tswgss14 221 BCE 秦王嬴政統一天下, 建立秦朝 https://www.youtube.com/watch?v=o3aKnCi1VdY 215 BCE 秦始皇派蒙恬北伐匈奴, 築長城 https://www.youtube.com/watch?v=sFBYnQQ9ul4