Three walls, four elephants and twenty-eight nights.

Three walls, four elephants and twenty-eight nights.

These three walls are Wei Zi Wall, Qiu Wall and Shi Tian Wall.

Ziweiyuan is the middle wall of three yuan, living in the center of the northern sky, so it is also called Zhonggong, or Ziweiyong. Wei Zi Palace means Imperial Palace, and most stars are named after official names.

Taiwei Courtyard is the upper wall of Sanyuan, located in the lower northeast of Ziwei Courtyard and south of Beidou.

The Shi Tian Wall is a three-dimensional lower wall, which is located in the southeast direction under the Wei Zi Wall, accounting for about 57 degrees in the sky, which is roughly equivalent to a part of the international common constellations such as the Five Immortals, the Giant Snake and the Snake, including 19 constellations.

Four elephants, the ancients imagined seven nights in the east, west, north and south as four animal images. Seven nights in the East Palace are like flying dragons in the air in early spring and early summer nights, so they are called "East Palace Black Dragon". The seven nights in the north appear as snakes and turtles in the night sky in summer and early autumn, so it is called "Gong Bei Xuan Wu"; The seven-night tiger in the west jumps out of the night sky in late autumn and early winter, so it is called "West Palace White Tiger"; Seven nights in the south are like a suzaku spreading its wings and flying, appearing in the night sky in winter and early spring, so it is called "Nangong Suzaku".