Since Nine, the highest single-digit number in base ten, stands for completeness and eternity, many emperors in the ancient China love the number a lot. ‘Nine Continents’ is used to describe the large territory of an empire. The emperors wore Nine-dragon Imperial Robes, ordered to construct Nine-dragon Walls and other buildings with relationship with number 9 in the imperial palaces, to show their great power, hope for longevity, and eternal reign of their empire.